Front Page Titles (by Subject) § 2.: There are Rational Principles of Action in Man - Selections from the Scottish Philosophy of Common Sense
The Online Library of Liberty
A project of Liberty Fund, Inc.
§ 2.: There are Rational Principles of Action in Man - Thomas Reid, Selections from the Scottish Philosophy of Common Sense 
Selections from the Scottish Philosophy of Common Sense, edited, with an introduction by G.A. Johnston (Chicago: Open Court, 1915).
About Liberty Fund:
Liberty Fund, Inc. is a private, educational foundation established to encourage the study of the ideal of a society of free and responsible individuals.
The text is in the public domain.
Fair use statement:
This material is put online to further the educational goals of Liberty Fund, Inc. Unless otherwise stated in the Copyright Information section above, this material may be used freely for educational and academic purposes. It may not be used in any way for profit.
There are Rational Principles of Action in Man
Mechanical principles of action produce their effect without any will or intention on our part. We may, by a voluntary effort, hinder the effect; but, if it be not hindered by will and effort, it is produced without them.
Animal principles of action require intention and will in their operation, but not judgment. They are, by ancient moralists, very properly called cæcæ cupidines, blind desires.
Having treated of these two classes, I proceed to the third—the rational principles of action in man; which have that name, because they can have no existence in beings not endowed with reason, and, in all their exertions, require, not only intention and will, but judgment or reason.
That talent which we call Reason, by which men that are adult and of a sound mind are distinguished from brutes, idiots, and infants, has, in all ages, among the learned and unlearned, been conceived to have two offices—to regulate our belief, and to regulate our actions and conduct.
Whatever we believe, we think agreeable to reason, and, on that account, yield our assent to it. Whatever we disbelieve, we think contrary to reason, and, on that account, dissent from it. Reason, therefore, is allowed to be the principle by which our belief and opinions ought to be regulated.
But reason has been no less universally conceived to be a principle by which our actions ought to be regulated.
To act reasonably, is a phrase no less common in all languages, than to judge reasonably. We immediately approve of a man’s conduct, when it appears that he had good reason for what he did. And every action we disapprove, we think unreasonable, or contrary to reason.
A way of speaking so universal among men, common to the learned and the unlearned in all nations and in all languages, must have a meaning. To suppose it to be words without meaning, is to treat, with undue contempt, the common sense of mankind.
Supposing this phrase to have a meaning, we may consider in what way reason may serve to regulate human conduct, so that some actions of men are to be denominated reasonable, and others unreasonable.
I take it for granted, that there can be no exercise of Reason without Judgment, nor, on the other hand, any judgment of things, abstract and general, without some degree of reason.
If, therefore, there be any principles of action in the human constitution, which, in their nature, necessarily imply such judgment, they are the principles which we may call rational, to distinguish them from animal principles, which imply desire and will, but not judgment.
Every deliberate human actions must be done either as the means, or as an end; as the means to some end, to which it is subservient, or as an end, for its own sake, and without regard to anything beyond it.
That it is a part of the office of reason to determine what are the proper means to any end which we desire, no man ever denied. But some philosophers, particularly Mr Hume, think that it is no part of the office of reason to determine the ends we ought to pursue, or the preference due to one end above another. This, he thinks, is not the office of reason, but of taste or feeling.
If this be so, reason cannot, with any propriety, be called a principle of action. Its office can only be to minister to the principles of action, by discovering the means of their gratification. Accordingly, Mr Hume maintains, that reason is no principle of action; but that it is, and ought to be, the servant of the passions.
I shall endeavour to shew that, among the various ends of human actions, there are some, of which, without reason, we could not even form a conception; and that, as soon as they are conceived, a regard to them is, by our constitution, not only a principle of action, but a leading and governing principle, to which all our animal principles are subordinate, and to which they ought to be subject.
These I shall call rational principles; because they can exist only in beings endowed with reason, and because, to act from these principles, is what has always been meant by acting according to reason.
The ends of human actions I have in view, are two—to wit, What is good for us upon the whole, and What appears to be our duty. They are very strictly connected, lead to the same course of conduct, and co-operate with each other; and, on that account, have commonly been comprehended under one name—that of reason. But, as they may be disjoined, and are really distinct principles of action, I shall consider them separately.1
[1 ]Ibid., pp. 579-580.