This partition between the faculties of understanding and sentiment, in all moral decisions, seems clear from the preceding hypothesis.  But I shall suppose that hypothesis false:  it will then be requisite to look out for some other theory that may be satisfactory; and I dare venture to affirm that none such will ever be found, so long as we suppose reason to be the sole source of morals.  To prove this, it will be proper t o weigh the five following considerations.

I. It is easy for a false hypothesis to maintain some appearance of truth, while it keeps wholly in generals, makes use of undefined terms, and employs comparisons, instead of instances.  This is particularly remarkable in that philosophy, which ascribes the discernment of all moral distinctions to reason alone, without the concurrence of sentiment.  It is impossible that, in any particular instance, this hypothesis can so much as be rendered intelligible, whatever specious figure it may make in general declamations and discourses.  Examine the crime of ingratitude, for instance; which has place, wherever we observe good-will, expressed and known, together with good-offices performed, on the one side, and a return of ill-will or indifference, with ill-offices or neglect on the other:  anatomize all these circumstances, and examine, by your reason alone, in what consists the demerit or blame.  You never will come to any issue or conclusion.

Reason judges either of matter of fact or of relations.  Enquire then, first, where is that matter of fact which we here call crime; point it out; determine the time of its existence; describe its essence or nature; explain the sense or faculty to which it discovers itself.  It resides in the mind of the person who is ungrateful.  He must, therefore, feel it, and be conscious of it.  But nothing is there, except the passion of ill-will or absolute indifference.  You cannot say that these, of themselves, always, and in all circumstances, are crimes.  No, they are only crimes when directed towards persons who have before expressed and displayed good-will towards us.  Consequently, we may infer, that the crime of ingratitude is not any particular individual fact; but arises from a complication of circumstances, which, being presented to the spectator, excites the sentiment of blame, by the particular structure and fabric of his mind.

This representation, you say, is false.  Crime, indeed, consists not in a particular fact, of whose reality we are assured by reason; but it consists in certain moral relations, discovered by reason, in the same manner as we discover by reason the truths of geometry or algebra.  But what are the relations, I ask, of which you here talk?  In the case stated above, I see first good-will and good-offices in one person; then ill-will and ill-offices in the other.  Between these, there is a relation of CONTARIETY.  Does the crime consist in that relation?  But suppose a person bore me ill-will or did me ill-offices; and I, in return, were indifferent towards him, or did him good offices.  Here is the same relation of contrariety; and yet my conduct is often highly laudable.  Twist and turn this matter as much as you will, you can never rest the morality on relation; but must have recourse to the decisions of sentiment.