David Hume is considered the greatest British philosopher and, through his influence on have been one of the major names in philosophy of the last 250 years. Kant famously said that Hume woke him from his “dogmatic slumber”. Though his first book, A Treatise of Human Nature, “fell dead-born from the press,” hardly noticed by anyone, it was a remarkable achievement, especially since it was written in his twenties. However, Hume’s views on religion saw him passed over for academic philosophy posts, and it was only his History of England and Political Discourses, published in his forties, that led to him becoming well known and well off.
An Enquiry Concerning Human Understanding is a mature version of the Treatise, and in its relatively easy, non-academic style is an excellent starting point for exploring Hume.
Hume start his enquiry by looking at the different species of philosophy. He brackets it into two species, one set of philosophers treat man as chiefly born for action and endeavour to cultivate his manners whereas another species consider man in the light of a reasonable rather than active being and instead endeavour to form his understanding. The members of the former species believe man to be influenced in his measures by taste and sentiment; pursuing one object, avoiding other, according to the value or virtue which these objects seems to possess. The other species regard human nature as a subject of speculation, and with a narrow scrutiny examine it, in order to find those principles, which regulate our understanding, excite our sentiments, and make us approve or blame any particular object, action of behaviour. Man being a reasonable being, receives from science proper food and nourishment for mind, but narrow bounds of science provides but little satisfaction. The author concedes that being an active man and from the various necessities of human life; he must submit to business and occupation. But the mind requires some relaxation, and cannot always support its bent to care and industry, so nature has pointed out a mixed kind of life as most suitable to human race. Indulge your passion for science, but let your science be human with direct reference to action and society. Abstruse thought and profound researches are prohibited in nature and would be punished by pensive melancholy and cold reception for those pretended discoveries. Be a philosopher; but amidst all your philosophy, be still a man. The author said that he would be happy, if we can unite the boundaries of the different species of philosophy, by reconciling profound enquiry with clearness, and truth with novelty.
Next the author outlays his theory of the origin of ideas. According to him the perceptions of the mind can again be divided into two species distinguished primarily by their different degrees of force and vivacity. A person can definitely feel the real pain of excessive heat, or the pleasure of moderate warmth. But when he afterwards recalls to his memory these sensations, or anticipates these by his imaginations, he never can entirely reach the force and vivacity of the original sentiment. Similarly when we reflect on our past sentiments and affections like fit of anger, our thought is a faithful mirror, and copies its object truly; but the colours which it employs are faint and dull in comparison of those in which our original perceptions were clothed. The author denominates the less forcible and lively of the mind perceptions as THOUGHTS or IDEAS. For the other species he employs the term IMPRESSIONS. By the term impression author means all our more lively perceptions, when we hear, or see, or love, or hate, or desire, or will. And impressions are distinguished from ideas, which are less lively perceptions, of which we’re conscious, when we reflect on any of these sensations.
The author further articulates that, at first view, nothing may seem more unbounded than the thought of man, which not only escapes all human power and authority, but is not even restrained within the limits of nature and reality. To form monsters, and join incongruous shapes and appearances, costs the imagination no more trouble than to conceive the most natural and familiar objects. And while the body is confined to one planet, along which it creeps with pain and difficulty; the thought can in an instant transport us into the most distant regions of the universe; or even beyond the universe, into the unbounded chaos, where nature is supposed to lie in total confusion. What never was seen, or heard of, may yet be conceived; nor is anything beyond the power of thought, except what implies an absolute contradiction. But though our thought seems to possess this unbounded liberty, upon a nearer examination, we find that all this creative power of the mind amounts to no more than the faculty of compounding, transposing, augmenting, or diminishing the materials afforded us by the senses and experience. When we think of a golden mountain, we only join two consistent ideas, gold and mountain with which we were formerly acquainted. In short, all the material of thinking are derived either from
our outward or inward sentiment: The mixture and composition of these belongs alone to the mind and will. For Hume, ancient and modern philosophers had all thought too highly of the powers of human reason. Great systems had been built to understand humans, God, and the universe, while forgetting that, ultimately, all we can know is what we observe directly through our five senses. Going completely against Descartes, Hume argued that there are no timeless, abstract ideas. Rather, all concepts are a second hand rendering of initial perceptions or impressions of things from our senses; we cannot have a notion of something until we have experienced it.
When we analyse our thoughts or ideas, however compounded or sublime we always find, that they resolve themselves into such simple ideas as were copied from a precedent feeling or sentiment. Even those ideas, which , at first view seem the most wide of this origin, are found, upon a nearer scrutiny, to be derived from it. The idea of God, as meaning an infinitely intelligent, wise, and good Being, arises from reflecting on the operations of our own mind, and augmenting, without limit, those qualities of goodness and wisdom. We may prosecute this enquiry to what length we please; where we shall always find, that every idea which we examine is copied from a similar impression. This is also proven from the fact that if from a defect of the organ, a man is not susceptible of any species of sensation, then he is also little susceptible of the corresponding ideas. A blind man can form no notion of colours; a deaf man of sounds. Restore them with that sense and you also open an inlet for the ideas; and they find no difficulty in conceiving these objects.
The author then propound his primary proposition that he believes can be used for any metaphysical reasonings. All ideas, especially abstract ones, are naturally faint and obscure: The mind has but a slender hold of them: They are apt to be confounded with other resembling ideas; and when we have often employed any term, though without a distinct meaning, we are apt to imagine it has a determinate idea, annexed to it. On the contrary, all impressions, that is, all sensations, either outward or inward, are strong and vivid: The limits between them are more exactly determined. When we entertain, therefore any suspicion, that a philosophical term is employed without any meaning or idea, we need to enquire, from what impression is that supposed idea derived?
Next Hume explores the principle of connexion between the different thoughts or ideas of the mind. To him, there appears to be only three principles of connexion among ideas, namely, Resemblance, Contiguity in time or place, and Cause and Effect. A picture naturally leads our thoughts to the original i.e. resemblance. The mention of one apartment in a building naturally introduces an enquiry or discourse concerning the others i.e. contiguity. And if we think of a wound, we can scarcely forbear reflecting on the pain which follows it i.e. cause and effect.
After the principles of connexion among ideas have been deduced, the author then tries to address sceptical doubts concerning the operations of the understanding. He suggests that all the objects of human reason or enquiry may naturally de divided into two kinds, Relations of Ideas, and Matters of Fact. Of the first kind are the sciences of Geometry, Algebra, and Arithmetic; and in short, every affirmation, which is either intuitively or demonstratively certain. That the square of the hypothenuse is equal to the square of the two sides, is a proposition, which expresses a relation between these figures. That three times five is equal to the half of thirty, expresses a relation between these numbers. Propositions of his kind are discoverable by the mere operation of thought, without dependence on what is anywhere existent in the universe. Though there never were a circle or triangle in nature, these truths would for ever retain their certainty and evidence. Matters of fact, which are the second objects of human reason, are not ascertained in the same manner; nor in our evidence of their truth, however great, of a like nature with the foregoing. The contrary of every matter of fact is still possible; because it can never imply a contradiction, and is conceived by the mind with the same facility and distinctness, as if ever so con formable to reality. That the sun will not rise tomorrow is no less intelligible a proposition, and implies no more contradiction, than the affirmation, that it will rise. We should in vain, therefore, attempt to demonstrate its falsehood. Were it demonstratively false, it would imply a contradiction, and could never be distinctly conceived by the mind.
The author further says that it may be a subject worthy of curiosity, to enquire what is the nature of evidence, which assures us of any real existence and matter of fact, beyond the present testimony of our senses, or the record of the memory. He suggests that all reasonings concerning matter of fact seem to be founded on the relation of Cause and Effect. By means of that alone we can go beyond the evidence of our memory and senses. There is always a connexion between the present fact and that which is inferred from it. Were there nothing to bind them together, the inference would be entirely precarious. Why? Because these are the effects of the human make and fabric, and closely connected with it. If we anatomize all the other reasonings of this nature, we shall find, that they are founded on the relation of cause and effect, and that this relation is either near or remote, direct or collateral. Heat and light are collateral effects of fire, and the one effect may justly be inferred from the other. If we would satisfy ourselves, therefore, concerning the nature of that evidence, which assures us of matters of fact, we must enquire how we arrive at the knowledge of cause and effect.
Here Hume venture to affirm, as a general proposition, that the knowledge of this relation is not, in any instance, attained by reasonings a priori; but arises entirely from experience, when we find, that any particular objects are constantly conjoined with each other. Let an object be presented to a man of ever so strong natural reason and abilities; if that object be entirely new to him, he will not be able to discover any of its cause or effects. Our reason, unassisted by experience, would never ever draw any inference concerning real existence and matter of fact. Hume’s proposition, that causes and effect are discoverable, not by reason, but by experience, still begs a further question i.e. What is the foundation of all conclusions from experience? As to past Experience, it can be allowed to give direct and certain information of those precise objects only, and that precise period of time, which fell under its cognizance: But why this experience should be extended to future times, and to other objects, which for aught we know, may be only in appearance similar? needs further enquiry.
Suppose a person, though endowed with the strongest faculties of reason and reflection, to be brought on a sudden into this world; he would, indeed, immediately observe a continual succession of objects, and one event following another; but he would not be able to discover any thing farther. He would not, at first, by any reasoning, be able to reach the idea of cause and effect; since the particular powers, by which all-natural operations are performed, never appear to the senses; nor is it reasonable to conclude, merely because one event, in one instance, precedes another, that therefore one is the cause, the other the effect. Their conjunction may be arbitrary and casual. There may be no reason to infer the existence of one from the appearance of the other. And in a word, such a person, without more experience, could never conjecture or reasoning concerning any matter of fact, or be assured of anything beyond what was immediately present to his memory and senses. Suppose again, that he has acquired more experience, and has lived so long in the world as to have observed similar objects or events to be constantly conjoined together; what is the consequence of this experience? He immediately infers the existence of one object from the appearance of the other. Yet he has not, by all his experience, acquired an idea or knowledge of the secret power, by which the one object produces the other, for example why a tiny seed produces a huge tree in few years? What is this principle that determines him to form such conclusion?
According to Hume, this principle is CUSTOM or HABIT. For wherever the repletion of any particular act or operation produces a propensity to renew the same act or operation, without being impelled by any reasoning or process of the understanding; this propensity is the effect of Custom. This definitely is not the ultimate reason of such propensity but has to be accepted as only a principle of human nature. The author at this point acknowledges that perhaps we can push our enquiries no farther, but must rest contended with it as ultimate principle, which we can assign, of all our conclusions from experience. According to author, it is sufficient satisfaction, that we can go only so far, without repining at the narrowness of our faculties, but at least we here advance a very intelligible proposition at least that we are determined by custom alone to expect the one e.g. heats from the appearance of the other e.g. flame. Custom, then is the great guide of human life. It is that principle alone, which renders our experience useful to us, and makes us expect, for the future, a similar train of events with those which have appeared in the past.
This is the essence of the book, there are more chapters on miracles, animals and liberty but explanations are more or less based on the philosophical framework articulated above. The author concludes the book by giving an explicit call to readers for rigor in philosophy and for all metaphysical works to be taken with a grain of salt. If we take in hand any volume; of divinity or school metaphysics, let us ask, does it contain any abstract reasoning concerning quantity or number? No. does it contain any experimental reasoning concerning matter of fact and existence? No. Commit it then to flames: For it can contain nothing but sophistry and illusion. This focus on relation of ideas and matter of fact made Hume a patron saint of every kind of philosophical school that stands for empiricism and disavows metaphysical speculation.
Hume observed that “All sciences have a relation, greater or less, to human nature.” We fool ourselves if we think that the natural sciences are an objective realm of knowledge outside humankind. In fact, by knowing human nature, Hume believed that you could create “a complete system of the sciences.” He felt that questions of logic, morals, and politics should be at least at the same level as natural science, and if he had been alive today he would no doubt have been a great supporter of psychology and the social sciences, because, as he put it in the Treatise, “The science of man is the only solid foundation for the other sciences.”