‘Episteme’ derives from the Ancient Greek word for ‘knowledge’ or ‘science’. Plato used the term to mean: justified or true knowledge, in contrast to mere opinion or belief. In the work of Foucault épistème has a somewhat different meaning: he makes it refer to a historical complex (or apparatus, or framework) of statements, assumptions, concepts, and fundamental ideas used – consciously as well as automatically – to define the kind of knowledge that is deemed possible. Thus, the episteme operates as a structure of thought. (Remember that Foucault at the Collège de France was professor of the ‘History of Systems of Thought’). Every historical time, and each culture, lives in its own truth-construction, its own set of rules to be followed in order to produce valid thought.

This doesn’t mean that all the humans of a certain period are, in an absolute sense, the prisoners of their episteme. Sometimes a ‘clearing’ (as Heidegger called it) is reached, as an opening to new discursive possibilities. Gaston Bachelard spoke of an ‘epistemological rupture’, which occurs whenever in the sciences the epistemological obstacles of a current episteme are being torn down, or burst under the influence of some new fundamental discovery. Because the episteme sometimes is a theory (concerning the conditions necessary for knowledge to be possible) it can be superseded by another theory; and because the episteme sometimes is a practice (a current way to define what statements in science and philosophy are possible), it is possible to break it. Of course epistemes also consist of tacit assumptions, which are not easy to recognise, nor to break away from.

It may be obvious by now that the concept of episteme as employed by Foucault does have a certain similarity to the notion of paradigm as Thomas Kuhn has used it. Kuhn seems to be most interested in the ‘paradigm’ that at a certain time is dominant in the world of science, and how then a shift in the dominant model of science occurs. Going back to its Greek origin, paradigm refers to a previous pattern which is held to be exemplary (in the sense that present patterns of thought or actions are measured against it). Kuhn used Newton’s Principia as an illustration of what he meant when speaking of a ‘paradigm’ in science: Newton offered a framework of concepts, procedures and results within which future work by other scientists was to be done, while, therefore, these scientists would have to adopt to the structuring influence of Newton’s framework. This makes a scientific paradigm a universally recognised scientific achievement that, for a time, provides model problems and solutions for a community of practitioners (to follow Kuhn’s own definition).

These scientists then operate within what is seen as, for the time being, ‘normal science’. This ‘normal science’ (the dominant practice in investigation and experimentation) has a conditioning and disciplining influence on one or more generations of scientific researchers. Evidence that falls outside the current paradigm, or contradicts it, will often be neglected. This, generally speaking, is not the result of ill will; a certain paradigm achieves its status as example and mould because it accords well with the then dominant way of viewing reality. Whatever falls outside the paradigm is an anomaly, not only for disturbing the dominant mould of science, but also for seeming to be out of step with the broadly accepted definition of reality in general. However, as the number of anomalies gradually grows, a point will be reached, sooner or later, when the dominant paradigm will, in a scientific revolution, be dethroned.

Foucault’s episteme is not restricted to the community of scientists, and its dominance may not at all be apparent. Several epistemes may exist simultaneously. Besides, whereas the assumptions inherent in the paradigm are part of the way science is practised, the assumptions in the episteme are more of a philosophic and linguistic nature: what can we know, and what can we speak of. These fundamental questions will receive very different answers before or after the Renaissance, before or after Kant and subjective rationalism, before or after Freud and psychology.