2009, In Bueno and Linnebo, eds., 'New Waves in Philosophy of Mathematics'
At the turn of the twentieth century, philosophers of mathematics were predominantly concerned with the foundations of mathematics. This followed the so-called "crisis of foundations" that resulted from the apparent need for in finitary sets in order to provide a proper foundation for mathematical analysis, and was exacerbated by the discovery of both apparent and actual paradoxes in naIve infinitary set theory (most famously, Russell's paradox). Philosophers and mathematicians at this time saw their job as to place mathematics on firm, and indeed certain, axiomatic foundations, so as to provide confidence in the new mathematics being developed. Thus, the "big three" foundational programmes of logicism, formalism, and intuitionism were established, each providing a different answer to the question of the proper interpretation of axiomatic mathematical theories. Now, 100 years on, philosophers are generally much less worried about the foundations of mathematics. Indeed, under the influence of W. V. Quine in particular, there has been a move away from "foundationalist" accounts of knowledge across the board. It is no longer assumed that there are any firm foundations on which to ground our beliefs. Against this backdrop, in the latter half of the twentieth century, philosophers of mathematics retreated from the question of how to establish the certainty of our mathematical knowledge to the question of whether we can claim to have any mathematical knowledge at all, even of our most foundational mathematical assumptions. Presented with Benacerraf's two challenges (1965, 1973) to the standard Platonist view of mathematical theories as assertions of truths about mathematical objects, it was no longer acceptable to assume without justification that we had any mathematical knowledge of such truths.