Scepticism is an ancient philosophical doctrine, and much of the theory of knowledge, epistemology, still vainly, or heroically depending upon your point of view, try's to slay this most perennial of demons. Scepticism has come in two broad types; scepticism with respect to the possibility of knowledge in principle and scepticism about the justifications made for knowledge.
In the pre-modern and modern eras scepticism had been revivified for largely political, as opposed to philosophical, reasons. Usually the second type was the most important variety so revived.
During the reformation and counter-reformation era in early modern Europe scepticism was dusted off as an ideological weapon to be used by the protagonists in what were quite evidently deeply political battles. During the early scientific revolution the traditional guardians of order in Europe were concerned that the scientific revolution might undermine political and religious, the two were often quite closely intertwined, authority as modern science tended to promote a largely naturalistic outlook.
So scepticism was resurrected once more as an ideological weapon, only this time it was employed against the view of the natural philosophers, usage of "science" was not widespread until the 19th century, that nature was a self-contained and autonomous entity operating on the basis of discernible physical laws.
Rene Descartes, in his Meditations on First Philosophy, sought to counter this sceptical trend by ascertaining the foundation upon which all of human knowledge rests. To find this foundation was to banish the demon. He argued that he had found this foundation after first doubting everything, even his own existence. Though most university philosophy courses adopt this as the starting point of modern philosophy in essence Descartes was engaged in an ideological, hence deeply political, project; namely defending science from the chorus of critics who brandished scepticism as a weapon against it. His foundation for all knowledge was to make the world safe for science.
Interestingly enough, a type of foundationalist programme received a great deal of impetus from the work of Gottlob Frege, who attempted to ground mathematical knowledge upon a firm logical foundation, in the late 19th century. Bertrand Russell had shown that Frege's work was incomplete, and Russell himself, alongside Alfred Whitehead, in a monumental work, attempted to fill the breach. David Hilbert at a now fabled turn of the century lecture in front of the world's most eminent mathematicians challenged the assembled, or anybody so interested, to base arithmetic on a firm axiomatic foundation. Hilbert was to resolutely declare, clearly looking askance at the sceptical temper, wir mussen wissen, wir werden wissen ("we must know, we will know"). Kurt Godel was to formally demonstrate, in the 1930s, that this programme could not succeed. Even in mathematics, as concerned as it is with systematic proof, foundationalism has been torn asunder.
One outgrowth, or spin-off, of this logical programme in the early 20th century was known as the philosophy of "logical positivism." The work of the Vienna Circle, as the logical positivists are sometimes referred to, can be characterised as one of history's grand attempts to make our world intelligible upon the basis of a single comprehensive world view. Though this programme ultimately failed we should not lightly dismiss the intellectual labour that went into building it.
The machine like mechanical philosophy of the early scientific revolution was another similar attempt that also ultimately failed (not that neoclassical economists have noticed).
The reaction to the failure of logical positivism has taken on many forms. One particularly pertinent one has been the rise of scepticism about science amongst some segments of the academic left, and the avant-garde intelligentsia more broadly, in the western world.
Armed with such terms as "incommensurability" and "paradigms" it was often asserted that science does not have sufficient warrant to back up many of its claims, and that science has no special place in the corpus of human knowledge. That is to say, all knowledge is relative. Scientific claims are no more valid than any other. Moreover, science does not progress to unearth deeper and deeper truth.
Science is largely a social institution and scientific change thereby occurs for social, rather than intellectual, reasons. Consensus amongst scientists is achieved through inherently social processes, and usually follows upon intense political battles amongst factions of scientists.
Furthermore the outlook of the logical positivists was necessarily politically reactionary. This is especially a claim often made in the critical theory, poststructuralist, and postmodernist literature. Yet some of the arch positivists of the 20th century, such as Bertrand Russell, Rudolf Carnap and Moritz Schlick were quite critical of political authority, social inequality, and great power politics. Recent scholarship has emphasised the cosmopolitan, as opposed to nationalist, nature of the political thinking of the Vienna Circle.