Having read as a teenager, and on his father’s advice, Spinoza’s Ethics and Principles According to Descartes, Popper concludes they are both:
‘… full of definitions which seemed to me arbitrary, pointless, and question-begging, so far as there was any question at all. It gave me a lifetime’s dislike of theorizing about God. (Theology, I still think, is due to lack of faith.)’
In Popper’s view, then, true faith stands alone. A commitment to theology, usually associated with only the most devout, has other connotations. A commitment to theology far from denoting the presence of true faith actually illustrates an element of doubt, of wavering of faithlessness.
Popper, Karl Unended Quest: An Intellectual Autobiography (London: Routledge Classics, 2005) p. 14.