Propositional attitudes (beliefs, desires) have always been one of the serious challenges of the modern philosophy of mind, and there is still a deep disagreement about the knowledge that should be warrantor for studying them. The reason is that as fundamental states of thought, unlike mental qualities or qualia (pain, perception), they are hardly subject to physical laws, because in addition to a kind of intentionality towards the world, they enjoy certain properties such as normativity, holism, and externalism, which are characteristics of Rationality. The first serious challenge to these attitudes in the field of Logic was raised by Russell and later by Carnap, who showed that these attitudes, due to their psychological characteristics, cannot satisfy the conditions of the two important principles of mathematical logic, namely, Extensionality and Atomicity. At the same time, their empiricism never allowed them to be referred to a "Third Realm", which it with the emergence of Quine's radical Naturalism, neuroscience took charge of them, and current Physicalism was fully accepted this shift. But a gap in Physicalism occurred with Davidson to create new capacities in relation to these attitudes. Davidson made mental attitudes as the signs of thought the fundamental foundation of his theory of Rationality, which was a middle ground between radical scientism and traditional modified rationalism, to prove that the realm of thought is supervenience to physics and represents the world with rational categories such as attitude and action. But rapid scientific advances have made this theory not pursued, and attitudes are now presented as the basis of an obsolete science called "Folk Psychology," which will eventually be abandoned like phlogiston by the replacement of precise scientific equivalents. So, for now, the fate of these attitudes is tied more to the future of neuroscience than to their rational nature.