‘Power to produce an effect supposes power not to produce it; otherwise it is not power but necessity, which is incompatible with power taken in a strict sense.... I am not able to form a conception how power (in the strict sense) can be exerted without will; nor can there be will without some degree of understanding. Therefore nothing can be an efficient cause in the proper sense but an intelligent being [_i.e._ a person]. Hence the only notion we can form of Almighty Power is, that God can do whatever He wills. Matter cannot be the cause of anything: it can only be an instrument in the hands of a real cause.... In physics the word cause has another meaning, which, though I think it an improper one, yet is distinct, and therefore may be reasoned upon. When a phenomenon is produced according to a certain law of nature, we call the law [or rule] the _cause_ of that phenomenon; and to the laws or rules of nature we accordingly ascribe power or efficiency. The whole business of physics is to discover, by observation and experiment, the laws of nature, and to apply them to the solution of phenomena. Now a law of nature is a purpose or resolution of the Author of nature to act according to a certain rule. There must be a real agent to produce the phenomenon according to the law. A malefactor is not hanged by the law, but by the executioner according to the law.’ Again:—‘A cause in the proper and strict sense signifies a _mind_ that has power and will to produce the effect. A cause in the physical sense means only something which, by the laws of nature, the effect always follows; as when we say that heat is the cause that turns water into vapour.... Between a physical cause and its effect the conjunction must be constant; unless in the case of a miracle. What D. Hume says of causes in general is very just when applied to physical causes—that a constant conjunction with the effect is essential to such causes, and implied in the very conception of them.’ Again:—‘I wish that the same general name—cause—had not been given to both. They differ _toto genere_. For a physical cause is not an agent. It does not act, but is acted upon. _You_ accordingly give them different names; calling the one the agent and not the cause, the other the cause and not the agent. But I think this too bold an innovation in language. Men have been so much accustomed to call the Deity the First Cause of things, that to maintain that He is no cause at all would be too shocking. To say that the world exists _without a cause_ would be accounted atheism, in spite of all explanations.... The words agent and action are less ambiguous. We say one _body_ acts upon another; and in vain would one attempt to abolish this language. To remedy this ambiguity of “cause” and