Butterfly effect

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https://en.wikipedia.org/wiki/Butterfly_effect

In chaos theory, the butterfly effect is the sensitive dependence on initial conditions in which a small change in one state of a deterministic nonlinear system can result in large differences in a later state.

The term is closely associated with the work of the mathematician and meteorologist Edward Norton Lorenz. He noted that the butterfly effect is derived from the example of the details of a tornado (the exact time of formation, the exact path taken) being influenced by minor perturbations such as a distant butterfly flapping its wings several weeks earlier. Lorenz originally used a seagull causing a storm but was persuaded to make it more poetic with the use of a butterfly and tornado by 1972. He discovered the effect when he observed runs of his weather model with initial condition data that were rounded in a seemingly inconsequential manner. He noted that the weather model would fail to reproduce the results of runs with the unrounded initial condition data. A very small change in initial conditions had created a significantly different outcome.

The idea that small causes may have large effects in weather was earlier acknowledged by the French mathematician and physicist Henri Poincaré. The American mathematician and philosopher Norbert Wiener also contributed to this theory. Lorenz's work placed the concept of instability of the Earth's atmosphere onto a quantitative base and linked the concept of instability to the properties of large classes of dynamic systems which are undergoing nonlinear dynamics and deterministic chaos.

The concept of the butterfly effect has since been used outside the context of weather science as a broad term for any situation where a small change is supposed to be the cause of larger consequences.

History

See also: Chaos theory § A popular but inaccurate analogy for chaos

In The Vocation of Man (1800), Johann Gottlieb Fichte says "you could not remove a single grain of sand from its place without thereby ... changing something throughout all parts of the immeasurable whole".

Chaos theory and the sensitive dependence on initial conditions were described in numerous forms of literature. This is evidenced by the case of the three-body problem by Poincaré in 1890. He later proposed that such phenomena could be common, for example, in meteorology.

In 1898, Jacques Hadamard noted general divergence of trajectories in spaces of negative curvature. Pierre Duhem discussed the possible general significance of this in 1908.

In 1950, Alan Turing noted: "The displacement of a single electron by a billionth of a centimetre at one moment might make the difference between a man being killed by an avalanche a year later, or escaping."

The idea that the death of one butterfly could eventually have a far-reaching ripple effect on subsequent historical events made its earliest known appearance in "A Sound of Thunder", a 1952 short story by Ray Bradbury in which a time traveller alters the future by inadvertently treading on a butterfly in the past.

More precisely, though, almost the exact idea and the exact phrasing —of a tiny insect's wing affecting the entire atmosphere's winds— was published in a children's book which became extremely successful and well-known globally in 1962, the year before Lorenz published:

"...whatever we do affects everything and everyone else, if even in the tiniest way. Why, when a housefly flaps his wings, a breeze goes round the world."

-- The Princess of Pure Reason

— Norton Juster, The Phantom Tollbooth

In 1961, Lorenz was running a numerical computer model to redo a weather prediction from the middle of the previous run as a shortcut. He entered the initial condition 0.506 from the printout instead of entering the full precision 0.506127 value. The result was a completely different weather scenario.

Lorenz wrote:

At one point I decided to repeat some of the computations in order to examine what was happening in greater detail. I stopped the computer, typed in a line of numbers that it had printed out a while earlier, and set it running again. I went down the hall for a cup of coffee and returned after about an hour, during which time the computer had simulated about two months of weather. The numbers being printed were nothing like the old ones. I immediately suspected a weak vacuum tube or some other computer trouble, which was not uncommon, but before calling for service I decided to see just where the mistake had occurred, knowing that this could speed up the servicing process. Instead of a sudden break, I found that the new values at first repeated the old ones, but soon afterward differed by one and then several units in the last [decimal] place, and then began to differ in the next to the last place and then in the place before that. In fact, the differences more or less steadily doubled in size every four days or so, until all resemblance with the original output disappeared somewhere in the second month. This was enough to tell me what had happened: the numbers that I had typed in were not the exact original numbers, but were the rounded-off values that had appeared in the original printout. The initial round-off errors were the culprits; they were steadily amplifying until they dominated the solution.

— E. N. Lorenz, The Essence of Chaos, University of Washington Press, Seattle (1993), page 134

In 1963, Lorenz published a theoretical study of this effect in a highly cited, seminal paper called Deterministic Nonperiodic Flow (the calculations were performed on a Royal McBee LGP-30 computer). Elsewhere he stated:

One meteorologist remarked that if the theory were correct, one flap of a sea gull's wings would be enough to alter the course of the weather forever. The controversy has not yet been settled, but the most recent evidence seems to favor the sea gulls.

A Battus polydamas butterfly in Brazil

Following proposals from colleagues, in later speeches and papers, Lorenz used the more poetic butterfly. According to Lorenz, when he failed to provide a title for a talk he was to present at the 139th meeting of the American Association for the Advancement of Science in 1972, Philip Merilees concocted Does the flap of a butterfly's wings in Brazil set off a tornado in Texas? as a title. Although a butterfly flapping its wings has remained constant in the expression of this concept, the location of the butterfly, the consequences, and the location of the consequences have varied widely.

The phrase refers to the effect of a butterfly's wings creating tiny changes in the atmosphere that may ultimately alter the path of a tornado or delay, accelerate, or even prevent the occurrence of a tornado in another location. The butterfly does not power or directly create the tornado, but the term is intended to imply that the flap of the butterfly's wings can cause the tornado: in the sense that the flap of the wings is a part of the initial conditions of an interconnected complex web; one set of conditions leads to a tornado, while the other set of conditions doesn't. The flapping wing creates a small change in the initial condition of the system, which cascades to large-scale alterations of events (compare: domino effect). Had the butterfly not flapped its wings, the trajectory of the system might have been vastly different—but it's also equally possible that the set of conditions without the butterfly flapping its wings is the set that leads to a tornado.

The butterfly effect presents an obvious challenge to prediction, since initial conditions for a system such as the weather can never be known to complete accuracy. This problem motivated the development of ensemble forecasting, in which a number of forecasts are made from perturbed initial conditions.

Some scientists have since argued that the weather system is not as sensitive to initial conditions as previously believed. David Orrell argues that the major contributor to weather forecast error is model error, with sensitivity to initial conditions playing a relatively small role. Stephen Wolfram also notes that the Lorenz equations are highly simplified and do not contain terms that represent viscous effects; he believes that these terms would tend to damp out small perturbations. Recent studies using generalized Lorenz models that included additional dissipative terms and nonlinearity suggested that a larger heating parameter is required for the onset of chaos.

While the "butterfly effect" is often explained as being synonymous with sensitive dependence on initial conditions of the kind described by Lorenz in his 1963 paper (and previously observed by Poincaré), the butterfly metaphor was originally applied to work he published in 1969 which took the idea a step further. Lorenz proposed a mathematical model for how tiny motions in the atmosphere scale up to affect larger systems. He found that the systems in that model could only be predicted up to a specific point in the future, and beyond that, reducing the error in the initial conditions would not increase the predictability (as long as the error is not zero). This demonstrated that a deterministic system could be "observationally indistinguishable" from a non-deterministic one in terms of predictability. Recent re-examinations of this paper suggest that it offered a significant challenge to the idea that our universe is deterministic, comparable to the challenges offered by quantum physics.

In the book entitled The Essence of Chaos published in 1993, Lorenz defined butterfly effect as: "The phenomenon that a small alteration in the state of a dynamical system will cause subsequent states to differ greatly from the states that would have followed without the alteration." This feature is the same as sensitive dependence of solutions on initial conditions (SDIC) in. In the same book, Lorenz applied the activity of skiing and developed an idealized skiing model for revealing the sensitivity of time-varying paths to initial positions. A predictability horizon is determined before the onset of SDIC.

Illustrations

The butterfly effect in the Lorenz attractor
time 0 ≤ t ≤ 30 (larger)		z coordinate (larger)
These figures show two segments of the three-dimensional evolution of two trajectories (one in blue, and the other in yellow) for the same period of time in the Lorenz attractor starting at two initial points that differ by only 10−5 in the x-coordinate. Initially, the two trajectories seem coincident, as indicated by the small difference between the z coordinate of the blue and yellow trajectories, but for t > 23 the difference is as large as the value of the trajectory. The final position of the cones indicates that the two trajectories are no longer coincident at t = 30.

Theory and mathematical definition

See also: Chaos theory § Lorenz's pioneering contributions to chaotic modeling

A plot of Lorenz' strange attractor for values ρ=28, σ = 10, β = 8/3. The butterfly effect or sensitive dependence on initial conditions is the property of a dynamical system that, starting from any of various arbitrarily close alternative initial conditions on the attractor, the iterated points will become arbitrarily spread out from each other.

Recurrence, the approximate return of a system toward its initial conditions, together with sensitive dependence on initial conditions, are the two main ingredients for chaotic motion. They have the practical consequence of making complex systems, such as the weather, difficult to predict past a certain time range (approximately a week in the case of weather) since it is impossible to measure the starting atmospheric conditions completely accurately.

A dynamical system displays sensitive dependence on initial conditions if points arbitrarily close together separate over time at an exponential rate. The definition is not topological, but essentially metrical. Lorenz defined sensitive dependence as follows:

The property characterizing an orbit (i.e., a solution) if most other orbits that pass close to it at some point do not remain close to it as time advances.

If M is the state space for the map ${\displaystyle f^t}$, then ${\displaystyle f^t}$ displays sensitive dependence to initial conditions if for any x in M and any δ > 0, there are y in M, with distance d(. , .) such that ${\displaystyle 0<d(x,y)<\delta }$ and such that

${\displaystyle d(f^{\tau }(x),f^{\tau }(y))>{\mathrm{e}}^{a\tau }d(x,y)}$

for some positive parameter a. The definition does not require that all points from a neighborhood separate from the base point x, but it requires one positive Lyapunov exponent. In addition to a positive Lyapunov exponent, boundedness is another major feature within chaotic systems.

The simplest mathematical framework exhibiting sensitive dependence on initial conditions is provided by a particular parametrization of the logistic map:

${\displaystyle x_{n+1}=4x_n(1-x_n),0\le x_0\le 1,}$

which, unlike most chaotic maps, has a closed-form solution:

${\displaystyle x_n={\sin }^2(2^n\theta \pi )}$

where the initial condition parameter ${\displaystyle \theta }$ is given by ${\displaystyle \theta =\frac{1}{\pi }{\sin }^{-1}(x_0^{1/2})}$. For rational ${\displaystyle \theta }$, after a finite number of iterations ${\displaystyle x_n}$ maps into a periodic sequence. But almost all ${\displaystyle \theta }$ are irrational, and, for irrational ${\displaystyle \theta }$, ${\displaystyle x_n}$ never repeats itself – it is non-periodic. This solution equation clearly demonstrates the two key features of chaos – stretching and folding: the factor 2ⁿ shows the exponential growth of stretching, which results in sensitive dependence on initial conditions (the butterfly effect), while the squared sine function keeps ${\displaystyle x_n}$ folded within the range [0, 1].

In physical systems

In weather

Overview

The butterfly effect is most familiar in terms of weather; it can easily be demonstrated in standard weather prediction models, for example. The climate scientists James Annan and William Connolley explain that chaos is important in the development of weather prediction methods; models are sensitive to initial conditions. They add the caveat: "Of course the existence of an unknown butterfly flapping its wings has no direct bearing on weather forecasts, since it will take far too long for such a small perturbation to grow to a significant size, and we have many more immediate uncertainties to worry about. So the direct impact of this phenomenon on weather prediction is often somewhat wrong."

Differentiating types of butterfly effects

The concept of the butterfly effect encompasses several phenomena. The two kinds of butterfly effects, including the sensitive dependence on initial conditions, and the ability of a tiny perturbation to create an organized circulation at large distances, are not exactly the same. In Palmer et al., a new type of butterfly effect is introduced, highlighting the potential impact of small-scale processes on finite predictability within the Lorenz 1969 model. Additionally, the identification of ill-conditioned aspects of the Lorenz 1969 model points to a practical form of finite predictability. These two distinct mechanisms suggesting finite predictability in the Lorenz 1969 model are collectively referred to as the third kind of butterfly effect. The authors in have considered Palmer et al.'s suggestions and have aimed to present their perspective without raising specific contentions.

The third kind of butterfly effect with finite predictability, as discussed in, was primarily proposed based on a convergent geometric series, known as Lorenz's and Lilly's formulas. Ongoing discussions are addressing the validity of these two formulas for estimating predictability limits in.

A comparison of the two kinds of butterfly effects and the third kind of butterfly effect has been documented. In recent studies, it was reported that both meteorological and non-meteorological linear models have shown that instability plays a role in producing a butterfly effect, which is characterized by brief but significant exponential growth resulting from a small disturbance.

Recent debates on butterfly effects

The first kind of butterfly effect (BE1), known as SDIC (Sensitive Dependence on Initial Conditions), is widely recognized and demonstrated through idealized chaotic models. However, opinions differ regarding the second kind of butterfly effect, specifically the impact of a butterfly flapping its wings on tornado formation, as indicated in two 2024 articles. In more recent discussions published by Physics Today, it is acknowledged that the second kind of butterfly effect (BE2) has never been rigorously verified using a realistic weather model. While the studies suggest that BE2 is unlikely in the real atmosphere, its invalidity in this context does not negate the applicability of BE1 in other areas, such as pandemics or historical events.

For the third kind of butterfly effect, the limited predictability within the Lorenz 1969 model is explained by scale interactions in one article and by system ill-conditioning in another more recent study.

Finite predictability in chaotic systems

According to Lighthill (1986), the presence of SDIC (commonly known as the butterfly effect) implies that chaotic systems have a finite predictability limit. In a literature review, it was found that Lorenz's perspective on the predictability limit can be condensed into the following statement:

• (A). The Lorenz 1963 model qualitatively revealed the essence of a finite predictability within a chaotic system such as the atmosphere. However, it did not determine a precise limit for the predictability of the atmosphere.
• (B). In the 1960s, the two-week predictability limit was originally estimated based on a doubling time of five days in real-world models. Since then, this finding has been documented in Charney et al. (1966) and has become a consensus.

Recently, a short video has been created to present Lorenz's perspective on predictability limit.

A recent study refers to the two-week predictability limit, initially calculated in the 1960s with the Mintz-Arakawa model's five-day doubling time, as the "Predictability Limit Hypothesis." Inspired by Moore's Law, this term acknowledges the collaborative contributions of Lorenz, Mintz, and Arakawa under Charney's leadership. The hypothesis supports the investigation into extended-range predictions using both partial differential equation (PDE)-based physics methods and Artificial Intelligence (AI) techniques.

In quantum mechanics

The potential for sensitive dependence on initial conditions (the butterfly effect) has been studied in a number of cases in semiclassical and quantum physics, including atoms in strong fields and the anisotropic Kepler problem. Some authors have argued that extreme (exponential) dependence on initial conditions is not expected in pure quantum treatments; however, the sensitive dependence on initial conditions demonstrated in classical motion is included in the semiclassical treatments developed by Martin Gutzwiller and John B. Delos and co-workers. The random matrix theory and simulations with quantum computers prove that some versions of the butterfly effect in quantum mechanics do not exist.

Other authors suggest that the butterfly effect can be observed in quantum systems. Zbyszek P. Karkuszewski et al. consider the time evolution of quantum systems which have slightly different Hamiltonians. They investigate the level of sensitivity of quantum systems to small changes in their given Hamiltonians. David Poulin et al. presented a quantum algorithm to measure fidelity decay, which "measures the rate at which identical initial states diverge when subjected to slightly different dynamics". They consider fidelity decay to be "the closest quantum analog to the (purely classical) butterfly effect". Whereas the classical butterfly effect considers the effect of a small change in the position and/or velocity of an object in a given Hamiltonian system, the quantum butterfly effect considers the effect of a small change in the Hamiltonian system with a given initial position and velocity. This quantum butterfly effect has been demonstrated experimentally. Quantum and semiclassical treatments of system sensitivity to initial conditions are known as quantum chaos.

In popular culture

Main article: Butterfly effect in popular culture

The butterfly effect has appeared across media such as literature (for instance, A Sound of Thunder), films and television (such as The Simpsons), video games (such as Life Is Strange), webcomics (such as Homestuck), musical references (such as "Butterfly Effect" by Travis Scott), AI-driven expansive language models, and more.

Antihumanism

From Wikipedia, the free encyclopedia

https://en.wikipedia.org/wiki/Antihumanism

In social theory and philosophy, antihumanism or anti-humanism is a theory that is critical of traditional humanism and its traditional ideas about humanity and the human condition. Central to antihumanism is the view that philosophical anthropology and its concepts of "human nature", "man" or "humanity" should be rejected as historically relative, ideological or metaphysical.

Origins

In the late 18th and 19th centuries, the philosophy of humanism was a cornerstone of the Enlightenment. Human history was seen as a product of human thought and action, to be understood through the categories of "consciousness", "agency", "choice", "responsibility", "moral values". Human beings were viewed as possessing common essential features. From the belief in a universal moral core of humanity, it followed that all persons were inherently free and equal. For liberal humanists such as Immanuel Kant, the universal law of reason was a guide towards total emancipation from any kind of tyranny.

Criticism of humanism as over-idealistic began in the 19th century. For Friedrich Nietzsche, humanism was nothing more than an empty figure of speech – a secular version of theism. Max Stirner expressed a similar position in his book The Ego and Its Own, published several decades before Nietzsche's work. Nietzsche argues in Genealogy of Morals that human rights exist as a means for the weak to constrain the strong; as such, they do not facilitate the emancipation of life, but instead deny it.

The young Karl Marx is sometimes considered an antihumanist, as he rejected the idea of human rights as a symptom of the very dehumanization they were intended to oppose. Given that capitalism forces individuals to behave in an egoistic manner, they are in constant conflict with one another, and are thus in need of rights to protect themselves. True emancipation, he asserted, could only come through the establishment of communism, which abolishes private property. According to many anti-humanists, such as Louis Althusser, mature Marx sees the idea of "humanity" as an unreal abstraction that masks conflicts between antagonistic classes; since human rights are abstract, the justice and equality they protect is also abstract, permitting extreme inequalities in reality.

In the 20th century, the view of humans as rationally autonomous was challenged by Sigmund Freud, who believed humans to be largely driven by unconscious irrational desires.

Martin Heidegger viewed humanism as a metaphysical philosophy that ascribes to humanity a universal essence and privileges it above all other forms of existence. For Heidegger, humanism takes consciousness as the paradigm of philosophy, leading it to a subjectivism and idealism that must be avoided. Like Hegel before him, Heidegger rejected the Kantian notion of autonomy, pointing out that humans were social and historical beings, as well as rejecting Kant's notion of a constituting consciousness. In Heidegger's philosophy, Being (Sein) and human Being (Dasein) are a primary unity. Dualisms of subject and object, consciousness and being, humanity and nature are inauthentic derivations from this. In the Letter on Humanism (1947), Heidegger distances himself from both humanism and existentialism. He argues that existentialism does not overcome metaphysics, as it merely reverses the basic metaphysical tenet that essence precedes existence. These metaphysical categories must instead be dismantled.

Positivism and scientism

Positivism is a philosophy of science based on the view that in the social as well as natural sciences, information derived from sensory experience, and logical and mathematical treatments of such data, are together the exclusive source of all authoritative knowledge. Positivism assumes that there is valid knowledge (truth) only in scientific knowledge. Obtaining and verifying data that can be received from the senses is known as empirical evidence. This view holds that society operates according to general laws that dictate the existence and interaction of ontologically real objects in the physical world. Introspective and intuitional attempts to gain knowledge are rejected. Though the positivist approach has been a recurrent theme in the history of Western thought, the concept was developed in the modern sense in the early 19th century by the philosopher and founding sociologist, Auguste Comte (1798-1857). Comte argued that society operates according to its own quasi-absolute laws, much as the physical world operates according to gravity and other absolute laws of nature.

Humanist thinker Tzvetan Todorov (1939-2017) identified within modernity a trend of thought which emphasizes science and within it tends towards a deterministic view of the world. He clearly identifies positivist theorist Auguste Comte as an important proponent of this view. For Todorov,

"Scientism does not eliminate the will but decides that since the results of science are valid for everyone, this will must be something shared, not individual. In practice, the individual must submit to the collectivity, which 'knows' better than he does. The autonomy of the will is maintained, but it is the will of the group, not the person […] scientism has flourished in two very different political contexts […] The first variant of scientism was put into practice by totalitarian regimes."

A similar approach emerges in the work associated with the Frankfurt School of social research. Antipositivism would be further facilitated by rejections of scientism; or science as ideology. Jürgen Habermas argues, in his On the Logic of the Social Sciences (1967), that

"the positivist thesis of unified science, which assimilates all the sciences to a natural-scientific model, fails because of the intimate relationship between the social sciences and history, and the fact that they are based on a situation-specific understanding of meaning that can be explicated only hermeneutically ... access to a symbolically prestructured reality cannot be gained by observation alone."

Structuralism

Structuralism was developed in post-war Paris as a response to the perceived contradiction between the free subject of philosophy and the determined subject of the human sciences. It drew on the systematic linguistics of Ferdinand de Saussure for a view of language and culture as a conventional system of signs preceding the individual subject's entry into them. In the study of linguistics the structuralists saw an objectivity and scientificity that contrasted with the humanist emphasis on creativity, freedom and purpose.

Saussure held that individual units of linguistic signification - signs - only enjoy their individuality and their power to signify by virtue of their contrasts or oppositions with other units in the same symbolic system. For Saussure, the sign is a mysterious unification of a sound and a thought. Nothing links the two: each sound and thought is in principle exchangeable for other sounds or concepts. A sign is only significant as a result of the total system in which it functions. To communicate by particular forms of speech and action (parole) is itself to presuppose a general body of rules (langue). The concrete piece of behaviour and the system that enables it to mean something mutually entail each other. The very act of identifying what they say already implies structures. Signs are thus not at the service of a subject; they do not pre-exist the relations of difference between them. We cannot seek an exit from this purely relational system. The individual is always subordinate to the code. Linguistic study must abstract from the subjective physical, physiological and psychological aspects of language to concentrate on langue as a self-contained whole.

The structuralist anthropologist Claude Levi-Strauss proclaimed that the goal of the human sciences was "not to constitute, but to dissolve man". He systematised a structuralist analysis of culture that incorporated ideas and methods from Saussure's model of language as a system of signifiers and signifieds. His work employed Saussurean technical terms such as langue and parole, as well as the distinction between synchronic analysis (abstracting a system as if it were timeless) and diachronic analysis (where temporal duration is factored in). He paid little attention to the individual and instead concentrated on systems of signs as they operated in primitive societies. For Levi-Strauss, cultural choice was always pre-constrained by a signifying convention. Everything in experience was matter for communication codes. The structure of this system was not devised by anyone and was not present in the minds of its users, but nonetheless could be discerned by a scientific observer.

The semiological work of Roland Barthes (1977) decried the cult of the author and indeed proclaimed his death.

Jacques Lacan's reformulation of psychoanalysis based on linguistics inevitably led to a similar diminishment of the concept of the autonomous individual: "man with a discourse on freedom which must certainly be called delusional...produced as it is by an animal at the mercy of language". According to Lacan, an individual is not born human but only becomes so through incorporation into a cultural order that Lacan terms The Symbolic. Access to this order proceeds by way of a "mirror stage", where a child models itself upon its own reflection in a mirror. Language allows us to impose order on our desires at this "Imaginary" stage of development. The unconscious, which exists prior to this Symbolic Order, must submit to the Symbolic Law. Since the unconscious is only accessible to the psychoanalyst in language, the most he or she can do is decode the conscious statements of the patient. This decoding can only take place within a signifying chain; the signified of unconscious discourse remains unattainable. It resides in a pre-signified dimension inaccessible to language that Lacan calls "The Real". From this, it follows that it is impossible to express subjectivity. Conscious discourse is the effect of a meaning beyond the reach of a speaking subject. The ego is a fiction that covers over a series of effects arrived at independently of the mind itself.

Taking a lead from Brecht's twin attack on bourgeois and socialist humanism, structural Marxist Louis Althusser used the term "antihumanism" in an attack against Marxist humanists, whose position he considered a revisionist movement. He believed humanism to be a bourgeois individualist philosophy that posits a "human essence" through which there is potential for authenticity and common human purpose. This essence does not exist: it is a formal structure of thought whose content is determined by the dominant interests of each historical epoch. Socialist humanism is similarly an ethical and thus ideological phenomenon. Since its argument rests on a moral and ethical basis, it reflects the reality of exploitation and discrimination that gives rise to it but never truly grasps this reality in thought. Marxist theory must go beyond this to a scientific analysis that directs to underlying forces such as economic relations and social institutions.

Althusser considered "structure" and "social relations" to have primacy over individual consciousness, opposing the philosophy of the subject. For Althusser, individuals are not constitutive of the social process, but are instead its supports or effects. Society constructs the individual in its own image through its ideologies: the beliefs, desires, preferences and judgements of the human individual are the effects of social practices. Where Marxist humanists such as Georg Lukács believed revolution was contingent on the development of the class consciousness of an historical subject - the proletariat - Althusser's antihumanism removed the role of human agency; history was a process without a subject.

Post-structuralism

Post-structuralist Jacques Derrida continued structuralism's focus on language as key to understanding all aspects of individual and social being, as well as its problematization of the human subject, but rejected its commitment to scientific objectivity. Derrida argued that if signs of language are only significant by virtue of their relations of difference with all other signs in the same system, then meaning is based purely on the play of differences, and is never truly present. He claimed that the fundamentally ambiguous nature of language makes human intention unknowable, attacked Enlightenment perfectionism, and condemned as futile the existentialist quest for authenticity in the face of the all-embracing network of signs. The world itself is text; a reference to a pure meaning prior to language cannot be expressed in it. As he stressed, "the subject is not some meta-linguistic substance or identity, some pure cogito of self-presence; it is always inscribed in language".

Michel Foucault challenged the foundational aspects of Enlightenment humanism. He rejected absolute categories of epistemology (truth or certainty) and philosophical anthropology (the subject, influence, tradition, class consciousness), in a manner not unlike Nietzsche's earlier dismissal of the categories of reason, morality, spirit, ego, motivation as philosophical substitutes for God. Foucault argued that modern values either produced counter-emancipatory results directly, or matched increased "freedom" with increased and disciplinary normatization. His anti-humanist skepticism extended to attempts to ground theory in human feeling, as much as in human reason, maintaining that both were historically contingent constructs, rather than the universals humanism maintained. In The Archaeology of Knowledge, Foucault dismissed history as "humanist anthropology". The methodology of his work focused not on the reality that lies behind the categories of "insanity", "criminality", "delinquency" and "sexuality", but on how these ideas were constructed by discourses.

Cultural examples

The heroine of the novel Nice Work begins by defining herself as a semiotic materialist, "a subject position in an infinite web of discourses – the discourses of power, sex, family, science, religion, poetry, etc." Charged with taking a bleak deterministic view, she retorts, "antihumanist, yes; inhuman, no...the truly determined subject is he who is not aware of the discursive formations that determine him". However, with greater life-experience, she comes closer to accepting that post-structuralism is an intriguing philosophical game, but probably meaningless to those who have not yet even gained awareness of humanism itself.