Although David Hume wrote on a number of different subjects, it would appear that his predominant interest was in the field of morals. It is easy to understand why this was true since morality as he conceived it lies in the background of all human activities. Man is not only a thinking being, as was emphasized by the Greek philosophers, but he is also a social and an active being and it is with this phase of his life that morality is concerned. It is involved in the political affairs of individuals and nations, and the same is true with reference to the social and religious life of any community of persons. Nothing is more important in the life of an individual or in the life of a nation than the moral standards by which life is governed. It was for reasons of this kind that Hume was especially anxious to make careful inquiry concerning the origin and nature of moral principles. Indeed it can be said that the subject of morality was closely related to all of the topics with which his various published works were concerned.
In the Treatise of Human Nature, which was Hume's first important publication, the first section of the book was devoted to an analysis of the human understanding. The purpose of this analysis was from one point of view only a preliminary step toward a more adequate interpretation of man's moral beliefs. Even in the History of England, which was written at a later date, there is presented an abundance of evidence to show that it is the morals of a nation which more than any other single factor determines its destiny. The significance of moral standards is emphasized again in the Essays on moral and political topics, which were so influential in establishing Hume's reputation as a scholar and an author. Finally, in the two books which he wrote on the subject of religion, the implications with reference to morals are especially prominent. The Enquiry Concerning the Principles of Morals was an attempt to place before the public in a more attractive style the materials that had been included in the third section of the Treatise of Human Nature.
Hume's philosophy of morals has a number of important characteristics which it may be helpful to bear in mind before one reads the Enquiry itself. One of these is the sharp distinction which is made between the fields of logic and ethics. Logic has to do with man's activities as a thinking being; ethics and morality are concerned with his actions as a social being. Logic is a matter of reasoning, and its function is to ascertain facts; morals has to do with the field of values and cannot be derived from a mere statement of facts. It is true that reasoning is involved in both logic and ethics, but while logic is derived from the nature of reason, ethics is not.
No amount of factual data, however complete it may be, is sufficient to tell one what it is that he ought to do. You cannot derive what ought to be from what is. It is only because humans are feeling creatures as well as thinking ones that value distinctions are possible and can indicate what it is that one ought to do. Failure to recognize these distinctions between the fields of facts and of values has in Hume's judgment been responsible for much of the confusion and the misunderstanding which has been characteristic of moral philosophy. By showing that moral judgments have their origin in the feelings rather than the intellect, he hopes to correct this situation. The procedure for determining facts is not the same as it is for recognizing distinctions of value.
Hume's position is in this respect similar to that of Immanuel Kant, who recognized the difference between what he called the pure, or theoretical, reason and the practical reason. The theoretical reason belongs to the understanding, and its function is to enable one to arrive at a true or correct knowledge of the facts. Practical reason is that particular function of the mind that enables one to know what it is that he ought to do. Theoretical reason is the work of the intellect, but practical reason pertains to the will, or that which moves people to act. It is true there are many points of contrast in the moral philosophies of Kant and Hume, for Kant was a rationalist in his conception of morals and Hume was not. However, they were in agreement insofar as they both recognized an important difference between judgments of fact and judgments of value.
One of the main reasons why Hume insisted that moral judgments are based on feelings rather than the intellect is that a mere awareness of facts is powerless to move one to act. People act as a result of their feelings and desires, and while it is true that these may be influenced by what they believe to be the facts, it is not the knowledge alone that moves the will or restrains it from acting. In the Treatise of Human Nature, Hume had said, "Tis not unreasonable for me to prefer the destruction of the whole world to the scratching of my finger." The purpose of this statement was to emphasize the fact that preferences, like all moral obligations, arise from the feelings and cannot be derived from a mere awareness of the facts.
Throughout all of his writings, Hume made use of the empirical method in his philosophy. Following the trend which had been established by such thinkers as Francis Bacon, John Locke, and George Berkeley, he held that all it is possible for anyone to know about themselves or the world in which they live must be derived from the facts of experience. There is no way of determining the nature of that which goes beyond the world of experience, and the belief in the possibility of such knowledge has been one of the main sources of dogmatism and the various forms of intolerance that have usually been associated with it.
In his analysis of the human understanding, Hume had applied the empirical method in order to find an explanation for the way in which ideas are formed. Like other empiricists who had preceded him, he assumed that all ideas are derived from sense impressions, but on the basis of this assumption he went beyond the work of his predecessors and denied the possibility of any genuine knowledge of anything that transcends the data which is supplied by the senses. This means that no one can have any knowledge of an external world, of a material substance, a spiritual substance, a self, or of God. While it was clear enough that one may believe in the reality of any or all of these objects, it was pointed out that there is no logical foundation for these beliefs nor for the existence of the objects to which they refer.
Strange as it may seem, this did not destroy the possibility of what is usually known as scientific knowledge. The so-called laws of nature are dependable at least to some degree even though they are only habits which have been formed in human minds on the basis of what has occurred in the past and the expectation that similar experiences will occur in the future.
Because he denied the possibility of knowing anything that goes beyond the realm of experience, Hume has often been regarded as a thoroughgoing skeptic. However, he did not deny the usefulness of the concepts that are employed in scientific procedure, but he did offer a new explanation of the way in which these concepts are formed. The principles that are involved in scientific procedure are only constructions of the human mind, but they are reliable insofar as they can be used successfully in the ordering of human experiences.
The use of the empirical method in the field of morals enabled Hume to show in a similar manner how it is that ideas concerning right and wrong conduct have come into existence. The conclusions reached in this area of experience were shocking to many of his contemporaries because they had long been accustomed to think of moral obligations as something that had been derived from some supreme authority and imposed on human beings by a power that was external to them. Whether this source of moral obligation was believed to be the will of God or derived from the nature of reason itself made little difference since the rules regulating conduct that were based upon it could be enforced by any political or ecclesiastical body that happened to be in power. This conception of morality was in Hume's opinion not only an unwarranted one but dangerous and at times injurious to the welfare of human beings. By showing that the principles of morality are not derived from an external authority but are drawn from the experiences of people, he believed he could present a far more accurate and satisfactory account of their origin and existence.
