Taylor’s question puts him on the terrain of “secularization” theory. But he introduces an important nuance by means of a three-fold taxonomy of “secular.”
1) (pp. 1-2) In classical or medieval accounts, the “secular” amounted to something like “the temporal”—the realm of “earthly” politics or of “mundane” vocations. This is the “secular” of the purported sacred/secular divide. The priest, for instance, pursues a “sacred” vocation, while the butcher, baker and candlestick maker are engaged in “secular” pursuits. Following Taylor, let’s call this secular1.
2) (pp. 2-3) In modernity, “secular” refers to a non-sectarian, neutral, and a-religious space or standpoint. We’ll refer to this as secular2. It is this notion of secular2 that is assumed both by the secularization thesis and normative secularism. According to secularization theory, as cultures experienced modernization and technological advancement, the (divisive) forces of religious belief and participation would wither in the face of modernity’s disenchantment of the world. According to secularism, political spaces (and the constitutions that create them) should carve out a realm purified of the contingency, particularity, and irrationality of religious belief and instead be governed by universal, neutral rationality. Secularism is always secularism2.
3) But Taylor helpfully articulates a third sense of the secular (secular3): a society is “secular3” insofar as religious belief or belief in God is understood to be one option among others, and thus contestable (and contested). At issue here is a shift in “the conditions of belief,” or what Peter Berger would call the “plausibility structures” of a society (detailing this “shift” is the focus of chapter 1). As Taylor notes, the shift to secularity “in this sense” indicates “a move from a society where belief in God is unchallenged and indeed, unproblematic, to one in which it is understood to be one option among others, and frequently not the easiest to embrace” (SA 3). It is in this sense that we live in a “secular age” even if religious participation might be visible and fervent. And it is in this sense that we could still entertain a certain “secularization3 thesis.” But this would be an account, not of how religion will wither in late modern societies, but rather of how and why the plausibility structures of such societies will make religion contestable (and contested). It will also make possible the emergence of “exclusive humanism” (p. 19).