Excerpt from David Hume, Treatise on Human Nature .  Public Domain. 

This excerpt is from BOOK III Of Morals, PART I Of virtue and vice in general SECT. I SECT. I MORAL DISTINCTIONS NOT DERIVed FROM REASON To read more of it in context, you may find the whole on Project Gutenberg or more conveniently with links to sections at http://www.class.uidaho.edu/mickelsen/ToC/hume%20treatise%20ToC.htm   You can also find it at http://socserv2.socsci.mcmaster.ca/~econ/ugcm/3ll3/hume/treat.html and on googlebooks.

I have bolded oak/elm/parricide, incest, and wilful murder so it will be easy to find the examples.

SECT. I MORAL DISTINCTIONS NOT DERIVed FROM REASON

Thus upon the whole, it is impossible, that the distinction betwixt moral good and evil, can be made to reason; since that distinction has an influence upon our actions, of which reason alone is incapable. Reason and judgment may, indeed, be the mediate cause of an action, by prompting, or by directing a passion: But it is not pretended, that a judgment of this kind, either in its truth or falshood, is attended with virtue or vice. And as to the judgments, which are caused by our judgments, they can still less bestow those moral qualities on the actions, which are their causes.

But to be more particular, and to shew, that those eternal immutable fitnesses and unfitnesses of things cannot be defended by sound philosophy, we may weigh the following considerations.

If the thought and understanding were alone capable of fixing the boundaries of right and wrong, the character of virtuous and vicious either must lie in some relations of objects, or must be a matter of fact, which is discovered by our reasoning. This consequence is evident. As the operations of human understanding divide themselves into two kinds, the comparing of ideas, and the inferring of matter of fact; were virtue discovered by the understanding; it must be an object of one of these operations, nor is there any third operation of the understanding. which can discover it. There has been an opinion very industriously propagated by certain philosophers, that morality is susceptible of demonstration; and though no one has ever been able to advance a single step in those demonstrations; yet it is taken for granted, that this science may be brought to an equal certainty with geometry or algebra. Upon this supposition. vice and virtue must consist in some relations; since it is allowed on all hands, that no matter of fact is capable of being demonstrated. Let us, therefore, begin with examining this hypothesis, and endeavour, if possible, to fix those moral qualities, which have been so long the objects of our fruitless researches. Point out distinctly the relations, which constitute morality or obligation, that we may know wherein they consist, and after what manner we must judge of them.

If you assert, that vice and virtue consist in relations susceptible of certainty and demonstration, you must confine yourself to those four relations, which alone admit of that degree of evidence; and in that case you run into absurdities, from which you will never be able to extricate yourself. For as you make the very essence of morality to lie in the relations, and as there is no one of these relations but what is applicable, not only to an irrational, but also to an inanimate object; it follows, that even such objects must be susceptible of merit or demerit. RESEMBLANCE, CONTRARIETY, DEGREES IN QUALITY, and PROPORTIONS IN QUANTITY AND NUMBER; all these relations belong as properly to matter, as to our actions, passions, and volitions. It is unquestionable, therefore, that morality lies not in any of these relations, nor the sense of it in their discovery.

[Footnote 13. As a proof, how confused our way of thinking on this subject commonly is, we may observe, that those who assert, that morality is demonstrable, do not say, that morality lies in the relations, and that the relations are distinguishable by reason. They only say, that reason can discover such an action, In such relations, to be virtuous, and such another vicious. It seems they thought it sufficient, if they could bring the word, Relation, into the proposition, without troubling themselves whether it was to the purpose or not. But here, I think, is plain argument. Demonstrative reason discovers only relations. But that reason, according to this hypothesis, discovers also vice and virtue. These moral qualities, therefore, must be relations. When we blame any action, in any situation, the whole complicated object, of action and situation, must form certain relations, wherein the essence of vice consists. This hypothesis is not otherwise intelligible. For what does reason discover, when it pronounces any action vicious? Does it discover a relation or a matter of fact? These questions are decisive, and must not be eluded.]

Should it be asserted, that the sense of morality consists in the discovery of some relation, distinct from these, and that our enumeration was not compleat, when we comprehended all demonstrable relations under four general heads: To this I know not what to reply, till some one be so good as to point out to me this new relation. It is impossible to refute a system, which has never yet been explained. In such a manner of fighting in the dark, a man loses his blows in the air, and often places them where the enemy is not present.

I must, therefore, on this occasion, rest contented with requiring the two following conditions of any one that would undertake to clear up this system. First, As moral good and evil belong only to the actions of the mind, and are derived from our situation with regard to external objects, the relations, from which these moral distinctions arise, must lie only betwixt internal actions, and external objects, and must not be applicable either to internal actions, compared among themselves, or to external objects, when placed in opposition to other external objects. For as morality is supposed to attend certain relations, if these relations coued belong to internal actions considered singly, it would follow, that we might be guilty of crimes in ourselves, and independent of our situation, with respect to the universe: And in like manner, if these moral relations coued be applied to external objects, it would follow, that even inanimate beings would be susceptible of moral beauty and deformity. Now it seems difficult to imagine, that any relation can be discovered betwixt our passions, volitions and actions, compared to external objects, which relation might not belong either to these passions and volitions, or to these external objects, compared among themselves. But it will be still more difficult to fulfil the second condition, requisite to justify this system. According to the principles of those who maintain an abstract rational difference betwixt moral good and evil, and a natural fitness and unfitness of things, it is not only supposed, that these relations, being eternal and immutable, are the same, when considered by every rational creature, but their effects are also supposed to be necessarily the same; and it is concluded they have no less, or rather a greater, influence in directing the will of the deity, than in governing the rational and virtuous of our own species. These two particulars are evidently distinct. It is one thing to know virtue, and another to conform the will to it. In order, therefore, to prove, that the measures of right and wrong are eternal laws, obligatory on every rational mind, it is not sufficient to shew the relations upon which they are founded: We must also point out the connexion betwixt the relation and the will; and must prove that this connexion is so necessary, that in every well-disposed mind, it must take place and have its influence; though the difference betwixt these minds be in other respects immense and infinite. Now besides what I have already proved, that even in human nature no relation can ever alone produce any action: besides this, I say, it has been shewn, in treating of the understanding, that there is no connexion of cause and effect, such as this is supposed to be, which is discoverable otherwise than by experience, and of which we can pretend to have any security by the simple consideration of the objects. All beings in the universe, considered in themselves, appear entirely loose and independent of each other. It is only by experience we learn their influence and connexion; and this influence we ought never to extend beyond experience.

Thus it will be impossible to fulfil the first condition required to the system of eternal measures of right and wrong; because it is impossible to shew those relations, upon which such a distinction may be founded: And it is as impossible to fulfil the second condition; because we cannot prove A PRIORI, that these relations, if they really existed and were perceived, would be universally forcible and obligatory.

But to make these general reflections more dear and convincing, we may illustrate them by some particular instances, wherein this character of moral good or evil is the most universally acknowledged.

Of all crimes that human creatures are capable of committing, the most horrid and unnatural is ingratitude, especially when it is committed against parents, and appears in the more flagrant instances of wounds and death. This is acknowledged by all mankind, philosophers as well as the people; the question only arises among philosophers, whether the guilt or moral deformity of this action be discovered by demonstrative reasoning, or be felt by an internal sense, and by means of some sentiment, which the reflecting on such an action naturally occasions. This question will soon be decided against the former opinion, if we can shew the same relations in other objects, without the notion of any guilt or iniquity attending them. Reason or science is nothing but the comparing of ideas, and the discovery of their relations; and if the same relations have different characters, it must evidently follow, that those characters are not discovered merely by reason. To put the affair, therefore, to this trial, let us chuse any inanimate object, such as an oak or elm; and let us suppose, that by the dropping of its seed, it produces a sapling below it, which springing up by degrees, at last overtops and destroys the parent tree: I ask, if in this instance there be wanting any relation, which is discoverable in parricide or ingratitude? Is not the one tree the cause of the other's existence; and the latter the cause of the destruction of the former, in the same manner as when a child murders his parent? It is not sufficient to reply, that a choice or will is wanting. For in the case of parricide, a will does not give rise to any DIFFERENT relations, but is only the cause from which the action is derived; and consequently produces the same relations, that in the oak or elm arise from some other principles. It is a will or choice, that determines a man to kill his parent; and they are the laws of matter and motion, that determine a sapling to destroy the oak, from which it sprung. Here then the same relations have different causes; but still the relations are the same: And as their discovery is not in both cases attended with a notion of immorality, it follows, that that notion does not arise from such a discovery.

But to chuse an instance, still more resembling; I would fain ask any one, why incest in the human species is criminal, and why the very same action, and the same relations in animals have not the smallest moral turpitude and deformity? If it be answered, that this action is innocent in animals, because they have not reason sufficient to discover its turpitude; but that man, being endowed with that faculty which ought to restrain him to his duty, the same action instantly becomes criminal to him; should this be said, I would reply, that this is evidently arguing in a circle. For before reason can perceive this turpitude, the turpitude must exist; and consequently is independent of the decisions of our reason, and is their object more properly than their effect. According to this system, then, every animal, that has sense, and appetite, and will; that is, every animal must be susceptible of all the same virtues and vices, for which we ascribe praise and blame to human creatures. All the difference is, that our superior reason may serve to discover the vice or virtue, and by that means may augment the blame or praise: But still this discovery supposes a separate being in these moral distinctions, and a being, which depends only on the will and appetite, and which, both in thought and reality, may be distinguished from the reason. Animals are susceptible of the same relations, with respect to each other, as the human species, and therefore would also be susceptible of the same morality, if the essence of morality consisted in these relations. Their want of a sufficient degree of reason may hinder them from perceiving the duties and obligations of morality, but can never hinder these duties from existing; since they must antecedently exist, in order to their being perceived. Reason must find them, and can never produce them. This argument deserves to be weighed, as being, in my opinion, entirely decisive.

Nor does this reasoning only prove, that morality consists not in any relations, that are the objects of science; but if examined, will prove with equal certainty, that it consists not in any matter of fact, which can be discovered by the understanding. This is the second part of our argument; and if it can be made evident, we may conclude, that morality is not an object of reason. But can there be any difficulty in proving, that vice and virtue are not matters of fact, whose existence we can infer by reason? Take any action allowed to be vicious: Wilful murder, for instance. Examine it in all lights, and see if you can find that matter of fact, or real existence, which you call vice. In which-ever way you take it, you find only certain passions, motives, volitions and thoughts. There is no other matter of fact in the case. The vice entirely escapes you, as long as you consider the object. You never can find it, till you turn your reflection into your own breast, and find a sentiment of disapprobation, which arises in you, towards this action. Here is a matter of fact; but it is the object of feeling, not of reason. It lies in yourself, not in the object. So that when you pronounce any action or character to be vicious, you mean nothing, but that from the constitution of your nature you have a feeling or sentiment of blame from the contemplation of it. Vice and virtue, therefore, may be compared to sounds, colours, heat and cold, which, according to modern philosophy, are not qualities in objects, but perceptions in the mind: And this discovery in morals, like that other in physics, is to be regarded as a considerable advancement of the speculative sciences; though, like that too, it has little or no influence on practice. Nothing can be more real, or concern us more, than our own sentiments of pleasure and uneasiness; and if these be favourable to virtue, and unfavourable to vice, no more can be requisite to the regulation of our conduct and behaviour.

I cannot forbear adding to these reasonings an observation, which may, perhaps, be found of some importance. In every system of morality, which I have hitherto met with, I have always remarked, that the author proceeds for some time in the ordinary way of reasoning, and establishes the being of a God, or makes observations concerning human affairs; when of a sudden I am surprized to find, that instead of the usual copulations of propositions, is, and is not, I meet with no proposition that is not connected with an ought, or an ought not. This change is imperceptible; but is, however, of the last consequence. For as this ought, or ought not, expresses some new relation or affirmation, it is necessary that it should be observed and explained; and at the same time that a reason should be given, for what seems altogether inconceivable, how this new relation can be a deduction from others, which are entirely different from it. But as authors do not commonly use this precaution, I shall presume to recommend it to the readers; and am persuaded, that this small attention would subvert all the vulgar systems of morality, and let us see, that the distinction of vice and virtue is not founded merely on the relations of objects, nor is perceived by reason.

SECT. II MORAL DISTINCTIONS DERIVed FROM A MORAL SENSE

Thus the course of the argument leads us to conclude, that since vice and virtue are not discoverable merely by reason, or the comparison of ideas, it must be by means of some impression or sentiment they occasion, that we are able to mark the difference betwixt them. Our decisions concerning moral rectitude and depravity are evidently perceptions; and as all perceptions are either impressions or ideas, the exclusion of the one is a convincing argument for the other. Morality, therefore, is more properly felt than judged of; though this feeling or sentiment is commonly so soft and gentle, that we are apt to confound it with an idea, according to our common custom of taking all things for the same, which have any near resemblance to each other.   .....

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