Today we know from experience how these tendencies implicit...

Today we know from experience how these tendencies implicit in the naturalist position itself have been developed, but in Hume, the whole trajectory is already indicated.

Naturalization of moral studies seems to demand a methodological reduction of the normative and the evaluative, which will end up being established as a definitive ontological reduction of human reason and freedom, which are mutually inseparable and inaccessible to the empirical method and never totally explained from strictly naturalist bases.

Thence are derived an emotivism and an irrationalism which threaten science itself insofar as its practical aspects are recognized along with its inability to produce absolutely certain knowledge. Hume assures that ‘We speak not strictly and philosophically when we talk of the combat of passion and of reason. Reason is, and ought only to be the slave of the passions, and can never pretend to any other office than to serve and obey them’[^16] .

Paradoxical though this may seem, this resignation that the practical should be the place for feelings derives from a reduced notion of reason, excessively bound up with a given idea of science and method and an extreme valuation of certainty. In Hume there is no renunciation of certainty, the basis of which is confided to habit, but one of reason. Predilection for certainty leads Hume to irrationalism, not to scepticism[^17] .

Karl Popper sums up the situation as follows, saying that, according to Hume, the scientific method is inductive, but: ‘... induction is completely invalid as an inference. There is not a shadow of a logical argument that would support the inference to a generalization from statements about the past (such as past repetitions of some 'evidence'). He [Hume] said that in spite of its lack of logical validity, induction plays an indispensable part in practical life [...] Thus there is a paradox.

Even our intellect does not work rationally '. [p.94] [...] This led Hume, one of the most reasonable thinkers of all time, to give up rationalism and look at man not as endowed with reason but as a product of blind habit. Acording to Russell this paradox of Hume's is responsible for the schizophrenia of modern man ’. [p.95][^18] If anything can be learnt for the present it is that we lack a notion of practical reason that is well structured and free of traditional errors.