Scottish philosopher. David Hume, who loses her father at the three years age, is raised by her mother, under the rigid control of her uncle, Pasteur.

In 1734, it leaves for France, where it writes its Treaty of the human nature, which will have little success. Secretary of a diplomat on mission on the continent of 1746 to 1750, it acquires a certain notoriety thanks to the Investigation into the human understanding. Its candidature for the pulpit of philosophy of Edinburgh and Glasgow having been refused, he becomes librarian about lawyers of Edinburgh.

From 1763 to 1766, it remains again in France, where, secretary of the ambassador of England, it is celebrated by the Parisian living rooms and the Encyclopedists. It is named under-secretary of State to London, in 1767, before turning over, in 1769, in its birthplace, where it dies in 1776.

Limits of the reason
All the company of Smells appears, in particular in the Dialogs on the natural religion, like a critic of the principle of reason: while admitting that there is an order of the things, the philosopher affirms that it is vain to seek to explain it while being based on the understanding. The examination of all the religious systems - i.e. of all cosmogonies - watch which it is not necessary to suppose that the cause of the world is an intelligent design. Can all be cause of the order (“Why an ordered system couldn't be woven belly as well as of the brain? ”), and when the reason wants to give an account of it she is mislaid in the arbitrary one.

The reason itself, underlines Hume, is a fact of the world, consequently “it is as little known to us as the instinct or the vegetation”. We can at most know his mechanism, not its base, and regulate the use within its natural limits of it. However, this vigilant regulation is essential, because the order of the spirit is generated disorder and tends to go back there. The reason is only imagination made uniform.  

The spirit passes naturally from an idea to another, but to the liking of the chance: no idea has by itself of exclusive affinity nor constant with another. The ideas are joined together according to the principles of association, which impose their rule on imagination: the spirit goes from an idea to another according to the easy transitions that the resemblance, the adjacency and causality constitute.  

A ceaseless fight thus opposes is delirious it and the principles which make imagination an organized faculty. The most subtle trick and most frightening of imagination consists in putting at its service the same principles which fix it, in particular the causality, of which it is seized to induce the most extravagant superstitions. It is what Hume names fiction, which results from an illegitimate use of the principles of the human nature.  

Belief and causality
To know always implies a going beyond given: when one formulates proposals such as “César was killed with the senate”, one believes in something that one did not see; in the same way, when it is said that “the sun will rise tomorrow”, it believes in something which, by definition, exceeds the experiment.

Among the principles, only causality makes it possible to conceive the idea of something to come, the idea of an effect to envisage or a probable cause. Causality (as principle) does not establish only one relation, it is also at the origin of the inference, founded on the repetition of the similar cases: after having noted several times a relation A-B (between the flame and heat, for example), from has one concludes B, and conversely. To infer, it is to expect something on the basis of experiment.  

However, it is not the experiment which can produce by itself its own going beyond: the repetition of same in the experiment leaves the events independent from/to each other. One could consider whereas it is the understanding which proceeds to the inference, that in fact the operations of the understanding supposes causality, i.e. the right to suppose that in the future an object will be related to another, as in the past. However Smells refuses this assumption by affirming that the repetition, which does not change anything in the things, modifies the spirit: this one is accustomed to the return of a phenomenon, it anticipates B if has occurs or supposes has if B is given. The spirit thus has a power to contract practices: experiment and practice are two principles of the human nature.  

When one speaks about causality, i.e. of a necessary connection, whereas it to us is given only one constant conjunction, one does nothing but follow one subjective tendency. Because connection necessary is in the spirit, not in the things, and it is there only like effect: the subject contemplates the repetitions in nature and tests in itself the modification which produced there; beyond the raw data, that Hume names impressions of feeling, it is the impression which still appears: what intervenes then, it is the impression of reflection, which, trusting the practice, supposes that the repetitions attested by the experiment will reproduce.  

The effect does not result from its cause like, in mathematics, the consequence of the principle; in causality, one allots to the effect a position of existence, and the negation of a fact does not imply contradiction; in fact, one can always consider that no heat accompanies a flame.  
 When one believes in the existence of a fact, one passes from a long-lived impression to the idea of a thing absent: the promptness of the impression is communicated to the idea under the terms of the principles of association. However it is always legitimate to wonder whether the practice which one contracts is founded on a constant repetition. Because imagination conceives false repetitions, in particular with the liking of passions, and the practice is then taken without reflection. If there is no means of preventing the error, one can however limit it: it is necessary to take care that the repetitions envisaged by the practice are confirmed by the theory of probability, which makes it possible to indicate the real repetitions, on the basis of their frequency.  

The thought and practice
Whereas the various impressions are with the base of any operation of the spirit, the always singular ideas, themselves, are only weak copies of the impressions. This resolution of the spirit in ultimate sensitive elements, which is specific to the psychological atomism of Smells, brings back the spirit to pure made existence, former to very thought.  

Pure timeless presence, the impression is the being which precedes the idea and thus remains in December of the thinkable one; it invests the spirit of reality, but at the same time it brings back any totality and any permanence to a fiction. For Smells, the unit of the world is only supposed, and the identity of Ego is imperceptible. However, our certainty practices that the world exists is quite as steadfast as our conviction to be one Me through the dissipation of the impressions. If we believe in it, it is because the operations of the understanding find their direction in practice and that they help us to live.  

Passions
To act, the man needs a passion, which seeks the pleasure, and flees the pain. There exist direct passions: the contemplation of a beautiful house gets joy, the spirit is turned then towards the pleasure. If I am owner of this house, I test pride of it; this other impression of reflection turns me towards the idea of Ego (in other cases towards the idea of others): it is an indirect passion. With that the reason does not have any share.  

In the action, the reason has of another role only to distinguish the useful one, the good means: it chooses the cause able to produce the desired effect. In fact, in fact passions pose the ends, which determine the desirable effects. Consequently, passions are of a nature radically different from that of the reason: whereas the means of action can be easily compared by the reason, the ends assigned with the action are undoubtedly incomparable data. Admittedly, there is a hierarchy of the ends - an action can be creditable or blameworthy -, but passions are not reasonable or unreasonable.  

Morals and esthetics
Like passions, morals depends by no means on the impotent reason. However, one could suppose that it is the reason which makes it possible to exceed the attachments particular and narrow created by passions and which makes possible, consequently, morals. However, actually, it is the imagination which reacts to the principles of passion: if need be, it makes play pleasure and pain out of their own legitimate exercise.  
 Whereas in the knowledge of an object we infer the known one with the unknown, left by part, affectivity reacts to the object as with a whole. Thus, the beauty is not in any the parts, it is a new effect produces in the spirit by the whole. The same applies to felt to the spectacle or tested sorrow or joy to the idea of an action. It is the taste which invests the things of our feelings and which “makes emerge a new creation”.  
 Passions, which are initially primarily partial, can thus extend to increasingly vast totalities. While the parts are in nature, totality is to be invented, in particular by the use of the artifice.  

Justice
Inventive truths are the legislators, who forge average “the obliques” of the human ends. Artificial virtue, justice is necessary because the benevolence is not spontaneously universal, and the distribution of the tangible properties is necessary because of their scarcity. It is socially useful that rules are laid down separating mine from the tien, if arbitrary they appear. The role of the government consists in giving to the general interest the promptness which it does not have of oneself.  

The general rules defined by the reason par excellence find their employment in the right, in particular in the regulation of the property. But the rules cannot be dictated by the utility, dependant on the private interest and opposite with the general interest which justice defends. The social convention is still of nature: our adhesion with the artifice supposes a passion which approves it.  

It is not only we do not make by pleasure, to even know. Thus, the reason is only “one marvellous and unintelligible instinct”, by report to which Hume privileges the practice: practical intellectual, moral, artistic, religious.  

Moderate skepticism that preaches Hume is not a resignation; on the contrary, it is a intellectual attitude which aims at exploiting the indefinitely rich field of the experiment. He seeks to fight the superstitions, i.e. the beliefs which are turned over against the life and it paralyze, with the complicity of the reason. This one, making a bad use of causality, usurps its rights: she claims to justify rationally what is only fiction resulting from metaphysics and the natural religion (which would proceed of the only natural light, i.e. the reason, and from the intimate conscience). Thus the open crisis begins from the rationalism which Hume, according to the expression of Kant, woke up of his “dogmatic sleep”.

Bibliography

1740 Treaty of the human nature  
1741-1783 moral, political and literary Tests  
1748 Test on the human understanding  
1751 Inquire into the principles of morals  
1762 History of England  
1779 Dialogs on the natural religion