In theoretical matters, ecclesiastical claims to knowledge have lead to various conflicts with science. Claims in orientational matters, sometimes connected to attempts to establish them as a rule for legislation, have often been in conflict with the justified claims of non-believers. In addition they violate the Principle of Autonomy of the individual, which is at the very heart of European identity so decisively shaped by the Enlightenment. The Principle of Autonomy implies that state legislation should not interfere in the life (...) of individual citizens, as long as his or her actions do not violate the rights of others. This paper—using the example of the theory of evolution—rejects ecclesiastical claims to theoretical knowledge as completely unfounded and preposterous. In the case of orientational knowledge—using the example of euthanasia—ecclesiastical claims to (universalizable) knowledge are shown to be unfounded as well. The Church’s position with respect to euthanasia and a range of other bio-ethical topics, such as pre-marital sex, contraception, abortion, indissolubility of marriage, and homosexuality, rests on a very peculiar ethical position. This ethical position is the natural right theory, which—far from being universalizable—is shared by very few people. Among other things, this position presupposes the belief in God as the creator of nature, and the assumption that ethical norms can be derived from this premise. Thus ecclesiastical knowledge claims, cannot be justified in a way which could be reasonably supposed to be universally acceptable. Kant (see the quote) was the first to require this sort of justification. Claims that fail to implement Kant’s stipulations should be eliminated by what I would like to call “Kant’s razor”. (shrink)