_Several Conditions._--Every act of memory involves these several conditions: 1. Present existence. 2. Past existence. 3. Mental activity at some moment of that past existence. 4. The recurrence to the mind of something thus thought, perceived, or felt. 5. Its recognition as a past or former thought or impression, and that our own. These last, the recurrence and the recognition, are strictly the essential elements of memory, yet the others are implied in it. In order to my remembering, for example, an occurrence of yesterday, I must exist at the present time, else I cannot remember at the present time; I must have existed yesterday, else there can be no memory of yesterday; my mind must have been active then, else there will be nothing to remember; the thoughts, perceptions, sensations, then occupying the mind, must now recur, else it is the same as if they had never been; they must recur, not as new thoughts and impressions, but as old ones, else I no longer remember, but only conceive or perceive. III. QUALITIES OF MEMORY. _Distinctions of Stewart and Wayland._--It has been customary to designate certain qualities as essential to a good memory. Susceptibility, retentiveness, and readiness, are thus distinguished by Mr. Stewart; the first denoting the facility with which the mind acquires; the second, the permanence with which it retains; and the third, the quickness with which it recalls and applies its original acquisitions. And these qualities are rarely united, he adds, in the same person. The memory which is susceptible and ready, is not commonly very retentive. Dr. Wayland makes the same distinction. Some men, he says, retain their knowledge more perfectly than they recall it. Others have their knowledge always at command. Some men acquire with great rapidity, but soon forget what they have learned. Others acquire with difficulty, but retain tenaciously. _Objections to this View._--Although supported by such authority, it admits of question whether this distinction is strictly valid. Facility of acquisition, the readiness with which the mind perceives truth, is hardly to be reckoned as an attribute of memory. It is a quality of mind, a quality possessed in diverse degrees by different persons, doubtless, but not a quality of mind in its distinctive capacity and office of _remembering_. It is no part, psychologically considered, of the function of _mental reproduction_. It is essential, indeed, to the act of memory that there should be something to remember, but the acquisition of the thing remembered, and the remembering, are two distinct and different mental acts; nor is it of any consequence to the mind, in remembering, whether the original acquisition was made with more or less facility. Indeed, so far as that bears upon the case at all, facility of acquisition, as even these writers admit, is likely to be rather a hindrance than a help to subsequent remembrance, since what is most readily acquired is not most readily recalled.