It is well known, however, that since Hume propounded his theory, all efficient causes have been discarded by a large class of philosophers. The senses take cognizance of nothing but the se- quence of events. One follows another. That which uniformly precedes, we call cause ; that which uniformly follows, we call the effect. As sequence is all the senses detect, that is all we have any right to assume. The idea that there is anything in the antecedent which determines the effect to be as it is and no other- wise, is altogether arbitrary. A cause, therefore, is nothing but an invariable antecedent, and an effect an invariable consequent.
Mr. Stuart Mill ^ modified Hume's definition of cause as Dr. Brown of Edinburgh had done before him. The former says, " It is necessary to our using the word cause, that we should believe not only that the antecedent always has been followed by the con- sequent, but tliat, as long as the present constitution of things en- dures, it always will be so." So Dr. Brown^ says, " A cause in the fullest definition which it philosophically admits of, may be said to be that which immediately precedes any change, and which, existing at any time in similar circumstances, has been always, and will be always immediately followed by a similar change." It is obvious that this definition is not only arbitrary, but that it is in- consistent with the fundamental principles of Hume's philosophy, and that of his followers, namely, that all our knowledge is founded on experience. Experience, relates to the past. It cannot guar-
1 Logic, p. 203. New York, 1855. '^ Inquiry, p. 17. Edinburgh, 1818.