In epistemology Rationalism is the view that regards reason as the chief source and test of knowledge. It holds that reality itself has an inherently logical structure and that a class of truths exists that the intellect can grasp directly. Accordingly there are certain rational principles—especially in logic and mathematics, and even in ethics and metaphysics—that are so fundamental that to deny them is to fall into contradiction. Rationalism is defined as a methodology or a theory “in which the criterion of the truth is not sensory but intellectual and deductive”. Deductive reasoning links premises with conclusions. If all premises are true, the terms are clear, and the rules of deductive logic are followed, then the conclusion reached is necessarily true. Rationalism has long been opposed to empiricism, the doctrine that all knowledge comes from, and must be tested by, sense experience. As against this doctrine, rationalism holds reason to be a faculty that can lay hold of truths beyond the reach of sense perception but only in terms of logical judgement. Therefore, rationalism has also been the rival of systems claiming esoteric knowledge, whether from mystical experience, revelation, or intuition, or that tend to stress the biological, the emotional or volitional, the unconscious, or the existential at the expense of the rational. Thus, particularly in politics rationalism has centred upon utilitarianism, secularism, and irreligion, absence, indifference, rejection of, or hostility towards religion, bringing it more in line with the worldly or materialist stylings of empiricism.