In his little book on Mind, he thus lays out his plan: "The attributes of the mind, which seem to be of a permanent nature, are here considered as 'properties' (intending such as perception, memory, &c.); those which are occasionally exerted and operate with effort as 'powers;' and those which may be perceived only occasionally, and which vary in degree or kind in different persons, as 'qualities.' As Reason and Will are 'properties' of the mind, and yet exerted as 'powers,' they are treated under both heads." OF IDEAS. "As I may not use the word in a customary sense, I think it right to explain what I mean by ideas. When I see a beautiful prospect illuminated by the sun, I have a _perception_ of light and shade. When, however, I have acquired such a knowledge of light and shade as to be able to represent on paper a spherical or many-sided body, I think I have acquired a knowledge of light and shade beyond that which the _mere_ remembrance of my perception would have produced. I shall, therefore, express myself as follows: Our knowledge consists of perceptions and deduction from them, which may be called ideas, opinions, thoughts. In reasoning, we employ these intellectual deductions, as we employ the perceptions of the facts themselves." OF ABSTRACTION. He observes: "It does not appear that we have the power of abstracting the mind from the consideration of any subject, except by engaging it in some other." OF BENEVOLENCE. "Benevolence is necessary, because it enlarges our sphere of happiness by rendering us participators in the happiness of others—besides producing, by sympathy, similar feelings in others." In a series of propositions on the exercise of mind, he impresses the mischief of admitting or indulging erroneous trains of thought, as illustrated by "the fears arising from bad management in childhood,—by persistence in vice after the gratification has ceased and the destruction certain; and also in contributing to the production of insanity." Or, on the other hand, he considers the _advantage_ of exercise in correct trains of thought; that the powers evinced by Newton, and, in certain cases, by Johnson, to have been unattainable, but as the result of such exercise. He enlarges on the moral effects of habitual increase of power in diverting the mind at will to other objects, and so subduing anger, mitigating calamity, &c. In illustrating the intensity that recurrence of impression is apt to give to the feelings, he says: "Benevolence indulged, leads to lasting friendship; whilst the harbouring sensations of even trivial disgust are too likely to develop animosity," &c. In speaking of the difficulty of ascertaining all the _facts_ and _feelings_ which enter into the formation of any one's opinions, he says: "It ought to incline us to think modestly of our own, and pay deference to those of others,"