Summary: A Treatise of Human Nature

Introduction

Hume's scepticism shines through from the very first lines of the Introduction: deploring that ignorance, which we still lie under in the most important questions, that can come before the tribunal of human reason, he believes that it is easy to perceive the weak foundation even of those systems, which have obtain'd the greatest credit, and have carry'd their pretensions highest to accurate and profound reasoning. And this is true even in the systems of the most eminent philosophers. In the end, such a situation seems to have drawn disgrace upon philosophy itself ¹.

The most obvious symptom of this crisis, of this failure, is the absence of any consensus. There is no agreement on anything: There is nothing which is not the subject of debate, and in which men of learning are not of contrary opinions. The most trivial question escapes not our controversy, and in the most momentous we are not able to give any certain decision. ².

It is metaphysics that is concerned by these endless debates:

From hence in my opinion arises that common prejudice against metaphysical reasonings of all kinds [...] We have so often lost our labour in such researches, that we commonly reject them without hesitation ³.

Here we are, in the end, led to a generalised scepticism, concerning all these endless questions: And indeed nothing but the most determin'd scepticism, along with a great degree of indolence, can justify this aversion to metaphysics ⁴.

This image of metaphysics as an endless battlefield would inspire Kant. It is found in the Critique of Pure Reason, from the first page of the preface to the first edition: The battlefield of these endless controversies is called metaphysics ⁵.

Far from wallowing in this admission of impotence, Hume seeks a way to resolve these problems, to put an end to these disagreements. To do this, we need to refocus our gaze on human nature: this must be the starting point of all our investigations.

In fact, ’Tis evident, that all the sciences have a relation, greater or less, to human nature; and that however wide any of them may seem to run from it, they still return back by one passage or another. Even Mathematics, Natural Philosophy, and Natural Religion, are in some measure dependent on the science of MAN; since they lie under the cognizance of men, and are judg'd of by their powers and faculties ⁶.

The term natural philosophy at this time refers to the natural sciences.

From man, here we are directed, more precisely, to the faculty that judges: the understanding.

Hume in turn takes a path blazed a generation earlier by Locke, in An Essay Concerning Human Understanding. Here is how he legitimises this decision:

’Tis impossible to tell what changes and improvements we might make in these sciences were we thoroughly acquainted with the extent and force of human understanding, and cou'd explain the nature of the ideas we employ, and of the operations we perform in our reasonings. ⁷.

While this investigation may be profitable for the sciences of objects which ultimately have only a remote relation to man, such as mathematics, natural philosophy or natural religion, it will be even more useful to sciences whose object is man himself, such as logic, morals, criticism (or aesthetics) and politics. Four sciences in which is comprehended almost every thing, which it can any way import us to be acquainted with ⁸.

Since there is not question of importance, whose decision is not compriz'd in the science of man; and there is none, which can be decided with any certainty, before we become acquainted with that science, then human nature is the only and true solid foundation of our knowledge: In pretending therefore to explain the principles of human nature, we in effect propose a compleat system of the sciences, built on a foundation almost entirely new, and the only one upon which they can stand with any security ⁹.

The method for such an essential science: experience and observation. Hume here displays his empiricism, which will make him in the eyes of posterity one of the leaders of this philosophical school: And as the science of man is the only solid foundation for the other sciences, so the only solid foundation we can give to this science itself must be laid on experience and observation. ¹⁰.

Hume pays tribute to his precursors, those before him who have begun to put the science of man on a new footing ¹¹. For all that, he explicitly mentions only Bacon, mentioning Locke only in an allusive formula: some late other philosophers in England, an honour to our native country ¹².

Naturally, he not only relies on the argument from authority by invoking these great minds, but legitimises the choice of the experimental method thus:

To me it seems evident, that the essence of the mind being equally unknown to us with that of external bodies, it must be equally impossible to form any notion of its powers and qualities otherwise than from careful and exact experiments, and the observation of those particular effects, which result from its different circumstances and situations.

And tho' we must endeavour to render all our principles as universal as possible, by tracing up our experiments to the utmost, and explaining all effects from the simplest and fewest causes, ’tis still certain we cannot go beyond experience; and any hypothesis, that pretends to discover the ultimate original qualities of human nature, ought at first to be rejected as presumptuous and chimerical ¹³.

"We cannot go beyond experience": here then is stated in all its clarity this founding principle of empiricism, which was to provoke many reactions in particular that of Kant, since he took it on board while claiming to go beyond it in the Critique of Pure Reason.

Hume concludes the introduction by mentioning a difficulty: in the field of morality, it is not possible to use the experimental method. We are not going to kill someone in order to prove the immoral nature of murder! Hume even advocates recourse to indirect experience in this case, in the form of a cautious observation of human life [...] in the common course of the world, by men's behaviour in company, in affairs, and in their pleasures ¹⁴. By collecting these observations in this way and comparing them, we can hope to witness the emergence of a moral science, more useful than any other discipline.

¹ A Treatise of Human Nature, Oxford University Press, 2007, Volume 1, Introduction, p.3
² Ibid.
³ Ibid.
⁴ Ibid.
⁵ Critique of Pure Reason, Cambridge University Press, Cambridge, 1998, Preface, p.99
⁶ A Treatise of Human Nature, Introduction, p.4
⁷ Ibid.
⁸ Ibid.
⁹ Ibid.
¹⁰ Ibid.
¹¹ P.5
¹¹ Ibid.
¹² Ibid.
¹³ Ibid.
¹⁴ p.6