Front Page Titles (by Subject) Appendix: Of Cause and Power - Selections from the Scottish Philosophy of Common Sense
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Appendix: Of Cause and Power - 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).
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Appendix: Of Cause and Power
It is proper here to explain what is meant by the cause of a phenomenon, when that word is used in natural philosophy. The word cause is so ambiguous, that I fear many mistake its meaning, and take it to mean the efficient cause, which I think it never does in this science.
By the cause of a phenomenon, nothing is meant but the law of nature, of which that phenomenon is an instance, or a necessary consequence. The cause of a body’s falling to the ground is its gravity. But gravity is not an efficient cause, but a general law, that obtains in nature, of which law the fall of this body is a particular instance. The cause why a body projected moves in a parabola, is, that this motion is the necessary consequence of the projectile force and gravity united. But these are not efficient causes; they are only laws of nature. In natural philosophy, therefore, we seek only the general laws, according to which nature works, and these we call the causes of what is done according to them. But such laws cannot be the efficient cause of anything. They are only the rule according to which the efficient cause operates.
A natural philosopher may search after the cause of a law of nature; but this means no more than searching for a more general law, which includes that particular law, and perhaps many others under it. This was all that Newton aimed at by his ether. He thought it possible, that, if there was such an ether, the gravitation of bodies, the reflection and refraction of the rays of light, and many other laws of nature, might be the necessary consequences of the elasticity and repelling force of the ether. But, supposing this ether to exist, its elasticity and repelling force must be considered as a law of nature; and the efficient cause of this elasticity would still have been latent.
Efficient causes, properly so called, are not within the sphere of natural philosophy. Its business is, from particular facts in the material world, to collect, by just induction, the laws that are general, and from these the more general, as far as we can go. And when this is done, natural philosophy has no more to do. It exhibits to our view the grand machine of the material world, analysed, as it were, and taken to pieces, with the connections and dependencies of its several parts, and the laws of its several movements. It belongs to another branch of philosophy to consider whether this machine is the work of chance or of design, and whether of good or of bad design; whether there is not an intelligent first Mover who contrived the whole, and gives motion to the whole, according to the laws which the natural philosopher has discovered, or, perhaps, according to laws still more general, of which we can only discover some branches; and whether he does these things by his own hand, so to speak, or employs subordinate efficient causes to execute his purposes. These are very noble and important inquiries, but they do not belong to natural philosophy; nor can we proceed in them in the way of experiment and induction, the only instruments the natural philosopher uses in his researches.
Whether you call this branch of philosophy Natural Theology or Metaphysics, I care not; but I think it ought not to be confounded with Natural Philosophy; and neither of them with Mathematics. Let the mathematician demonstrate the relation of abstract quantity; the natural philosopher investigate the laws of the material system by induction; and the metaphysician, the final causes, and the efficient causes of what we see and what natural philosophy discovers in the world we live in.
As to final causes, they stare us in the face wherever we cast our eyes. I can no more doubt whether the eye was made for the purpose of seeing, and the ear of hearing, than I can doubt of a mathematical axiom; yet the evidence is neither mathematical demonstration, nor is it induction. In a word, final causes, good final causes, are seen plainly everywhere: in the heavens and in the earth; in the constitution of every animal, and in our own constitution of body and of mind; and they are most worthy of observation, and have a charm in them that delights the soul.
As to efficient causes, I am afraid our faculties carry us but a very little way, and almost only to general conclusions. I hold it to be self-evident, that every production, and every change in nature, must have an efficient cause that has power to produce the effect; and that an effect which has the most manifest marks of intelligence, wisdom, and goodness, must have an intelligent, wise, and good efficient cause. From these, and some such self-evident truths, we may discover the principles of natural theology, and that the Deity is the first efficient cause of all nature. But how far he operates in nature immediately, or how far by the ministry of subordinate efficient causes, to which he has given power adequate to the task committed to them, I am afraid our reason is not able to discover, and we can do little else than conjecture. We are led by nature to believe ourselves to be the efficient causes of our own voluntary actions; and, from analogy, we judge the same of other intelligent beings. But with regard to the works of nature, I cannot recollect a single instance wherein I can say, with any degree of assurance, that such a thing is the efficient cause of such a phenomenon of nature.
I never could see good reason to believe that matter has any active power at all. And, indeed, if it were evident that it has one, I think there could be no good reason assigned for not allowing it others. Your Lordship speaks of the power of resisting motion, and some others, as acknowledged active powers inherent in matter. As to the resistance to motion, and the continuance in motion, I never could satisfy myself whether these are not the necessary consequences of matter being inactive. If they imply activity, they may lie in some other cause.
I am not able to form any distinct conception of active power but such as I find in myself. I can only exert my active power by will, which supposes thought. It seems to me, that, if I was not conscious of activity in myself, I could never, from things I see about me, have had the conception or idea of active power. I see a succession of changes, but I see not the power, that is, the efficient cause of them; but, having got the notion of active power, from the consciousness of my own activity, and finding it a first principle, that every production requires active power, I can reason about an active power of that kind I am acquainted with—that is, such as supposes thought and choice, and is exerted by will. But, if there is anything in an unthinking inanimate being that can be called active power, I know not what it is, and cannot reason about it.
If you conceive that the activity of matter is directed by thought and will in matter, every particle of matter must know the situation and distance of every other particle within the planetary system; but this, I am apt to think, is not your Lordship’s opinion.
I must therefore conclude, that this active power is guided in all its operations by some intelligent Being, who knows both the law of gravitation, and the distance and situation of every particle of matter with regard to every other particle, in all the changes that happen in the material world. I can only conceive two ways in which this particle of matter can be guided, in all the exertions of its active power, by an intelligent Being. Either it was formed, in its creation, upon a foreknowledge of all the situations it shall ever be in with respect to other particles, and had such an internal structure given it, as necessarily produces, in succession, all the motions, and tendencies to motion, it shall ever exert. This would make every particle of matter a machine or automaton, and every particle of a different structure from every other particle in the universe. This is indeed the opinion of Leibnitz; but I am not prejudiced against it upon that account; I only wished to know whether your Lordship adopted it or not. Another way, and the only other way, in which I can conceive the active power of a particle of matter, guided by an intelligent Being, is by a continual influence exerted according to its situation and the situation of other particles. In this case, the particle would be guided as a horse is by his rider; and I think it would be improper to ascribe to it the power of gravitation. It has only the power of obeying its guide. Whether your Lordship chooses the first or the last in this alternative, I should be glad to know; or whether you can think of a third way better than either.1
The ambiguity of the words power, cause, agent, and of all the words related to these, tends to perplex this question. The weakness of human understanding, which gives us only an indirect and relative conception of power, contributes to darken our reasoning, and should make us cautious and modest in our determinations.
We can derive little light in this matter from the events which we observe in the course of nature. We perceive changes innumerable in things without us. We know that those changes must be produced by the active power of some agent; but we neither perceive the agent nor the power, but the change only. Whether the things be active, or merely passive, is not easily discovered. And though it may be an object of curiosity to the speculative few, it does not greatly concern the many.
From the course of events in the natural world, we have sufficient reason to conclude the existence of an eternal intelligent First Cause. But whether He acts immediately in the production of those events, or by subordinate intelligent agents, or by instruments that are unintelligent, and what the number, the nature, and the different offices, of those agents or instruments may be—these I apprehend to be mysteries placed beyond the limits of human knowledge. We see an established order in the succession of natural events, but we see not the bond that connects them together.
Since we derive so little light, with regard to efficient causes and their active power, from attention to the natural world, let us next attend to the moral, I mean to human actions and conduct.
When I observe a plant growing from its seed to maturity, I know that there must be a cause that has power to produce this effect. But I see neither the cause nor the manner of its operation.
But, in certain motions of my body and directions of my thought, I know not only that there must be a cause that has power to produce these effects, but that I am that cause; and I am conscious of what I do in order to the production of them.
From the consciousness of our own activity, seems to be derived not only the clearest, but the only conception we can form of activity, or the exertion of active power.
As I am unable to form a notion of any intellectual power different in kind from those I possess, the same holds with respect to active power. If all men had been blind, we should have had no conception of the power of seeing, nor any name for it in language. If man had not the powers of abstraction and reasoning, we could not have had any conception of these operations. In like manner, if he had not some degree of active power, and if he were not conscious of the exertion of it in his voluntary actions, it is probable he could have no conception of activity, or of active power.
A train of events following one another ever so regularly, could never lead us to the notion of a cause, if we had not, from our constitution, a conviction of the necessity of a cause to every event.
And of the manner in which a cause may exert its active power, we can have no conception, but from consciousness of the manner in which our active power is exerted.
Every man is led by nature to attribute to himself the free determinations of his own will, and to believe those events to be in his power which depend upon his will. On the other hand, it is self-evident, that nothing is in our power that is not subject to our will.
We grow from childhood to manhood, we digest our food, our blood circulates, our heart and arteries beat, we are sometimes sick and sometimes in health; all these things must be done by the power of some agent; but they are not done by our power. How do we know this? Because they are not subject to our will. This is the infallible criterion by which we distinguish what is our doing from what is not; what is in our power from what is not.
Human power, therefore, can only be exerted by will, and we are unable to conceive any active power to be exerted without will. Every man knows infallibly that what is done by his conscious will and intention, is to be imputed to him, as the agent or cause; and that whatever is done without his will and intention, cannot be imputed to him with truth.
We judge of the actions and conduct of other men by the same rule as we judge of our own. In morals, it is self-evident that no man can be the object either of approbation or of blame for what he did not. But how shall we know whether it is his doing or not? If the action depended upon his will, and if he intended and willed it, it is his action in the judgment of all mankind. But if it was done without his knowledge, or without his will and intention, it is as certain that he did it not, and that it ought not to be imputed to him as the agent.
Now it is evident that, to constitute the relation between me and my action, my conception of the action, and will to do it, are essential. For what I never conceived nor willed, I never did.
If any man, therefore, affirms, that a being may be the efficient cause of an action, and have power to produce it, which that being can neither conceive nor will, he speaks a language which I do not understand. If he has a meaning, his notion of power and efficiency must be essentially different from mine; and, until he conveys his notion of efficiency to my understanding, I can no more assent to his opinion than if he should affirm that a being without life may feel pain.
It seems, therefore, to me most probable, that such beings only as have some degree of understanding and will, can possess active power; and that inanimate beings must be merely passive, and have no real activity. Nothing we perceive without us affords any good ground for ascribing active power to any inanimate being; and everything we can discover in our own constitution, leads us to think that active power cannot be exerted without will and intelligence.1
THE OPERATIONS OF THE MIND
[1 ]“Letter to Lord Kames,” 16th Dec. 1780 (Works, vol. i. pp. 56-59).
[1 ]“Essays on the Active Powers of Man” (Works, vol. ii. pp. 522-525).