The presented paper describes the phenomenon of secularisation and secularism in the culture of Western Europe, and attempts to identify its sources. The first point of the paper, The meaning of secularization and secularism, explains secularisation as a social process in which religion or, more strictly, religious institutes, religious behaviour, and religiously inspired conscience, are gradually losing their control over many fields of social activity such like education, arts or politics. Secularisation can be labelled as a philosophy of life “as if there were no God”, or a kind of ideology that tries to justify not only the very fact of secularisation but declares it a source and norm for human progress and demands the proclamation of man’s absolute autonomy in shaping his own destination. Among many philosophers who have influenced development of secularisation and secularism two stand out: R. Descartes (second point) and F. Nietzsche (third point). In the philosophy of Descartes one can identify at least four sources of modern secularism. These are: his concept of philosophy, theory of cognition with the resulting departure from classical concepts of truth and rationality and development of alternative ones, Cartesian metaphysics and the arguments for the existence of God and his concept of the nature of God evolving from those arguments. The last part of the article presents Nietzsche’s move away from the faith in Christian God and his turn to atheism. At least three fundamental causes for Nietzsche’s radical autosecularisation can be discerned: the emotional religion of his home, his disbelief in the authenticity of the Bible and his growing familiarity with the philosophy of Schopenhauer.

The distinction between primary and secondary qualities, most famously outlined by Galileo, and subsequently supported, inter alia, by Descartes and by Locke, has widely been considered one of the crucial factors in the development of modern idealism. In its contemporary form, the distinction identifies some of the perceived properties as mental phenomena due to their content and structural dependence on the mind. However, this account of the primary/secondary distinction is largely different from its original version developed by the above-mentioned philosophers, within whose work the mental being of the perceived qualities was demonstrated objectively, from the conceptually-derived nature of matter, and not subjectively, by referring to the mind’s participation in the cognitive process. It was only at the next stage of the early modern subjectivisation of sense perception, best exemplified by such philosophers as Arnold Geulincx and Richard Burthogge, that the creative role played by the mind in sensation and, consequently, the mind-dependency of the sensible qualities was recognised – a turn influenced by the reinterpretation of Aristotelian philosophy offered by Jacopo Zabarella and the Paduan school, as well as by anti-Aristotelianism of the kind developed in Netherlands. Furthermore, the two different approaches to the primary/ secondary distinction can be linked with two main types of post-Cartesian idealism, i.e. Berkeleian and Kantian – a claim for which illustrative evidence from British philosophy, namely from Berkeley’s and Burthogge’s respective theories, can be drawn.