from an object is transferred to the optic nerve in a manner similar to the transmission of force from one object to another when motions of other kinds are produced, seems a reasonable explanation of the conditions for vision. But this is not sight. Light from an object makes an impression on the sensitized plate of a camera. But we do not say the camera sees the object. The question may

be asked how we know the camera does not see the object. Such a question is sometimes put as if to throw doubt on the distinction made between mental energy and physical force. But it is rather an evidence of the necessity for the distinction. The very asking of the question shows that no one is so bold as to say that the physical impression is sight. The question assumes that for sight to be possible there must be some power of consciousness in the camera to perceive, and the thing asked for is how we know there is not this consciousness there. In order to produce any perception there must be not only an impression, such as that of light on the sensitized plate, but an activity comparing this with other impressions of the past, and such a comparison always implies mind as its source. The activity of perception, then, can be traced to mind and no further. The moment we leave conscious mind we get no activity of perception.

If perception is a native activity, then all the higher exercises of consciousness are native activities. In the first place, they all depend on the perceptions, and without the native activity of perception they could not exist. In the second place, whatever is peculiar to these activities, that is, whatever belongs to them apart from perception, can only be traced to inherent powers of the mind. After perception, there is no element of power introduced from abroad. In the third place, the same element of comparison which is found in perception is found as an

by a higher unity instead of leaving them to burden the memory by the laws of association alone. The names of objects and classes of objects should be made thoroughly familiar as early as possible, as representatives of unities; and general statements that need to be proved, such as the propositions of Geometry, if they can be understood by themselves, should be learned before the demonstration is studied, that discrimination may be brought under the proper unity from the first.

(II.) Criticism that ends with the destruction of that which is criticised is without value. A critic may compel a better construction by destructive criticism; but the good is indirectly done, unless criticism leads to comparisons of a more correct character, and thus directs the unifying powers. The critic who indulges in destructive criticism mainly, fails to develop in himself a broad and strong intellect. Construction should succeed destruction, and supply the antecedent reason for it. We take down and remove that we may have a place for a new and better structure.

CHAPTER VI.

CORRELATION AND DEGRADATION.

HE term correlation as used here is borrowed from its use in physics. When the blacksmith's hammer comes down upon a piece of iron, the motion of the hammer is arrested and heat is produced. The muscular force of the arm imparts motion to the hammer, and the hammer produces heat. Heat is not produced till the motion of the hammer ceases, and the motion is not produced till the muscular energy is expended. So long as the energy is inactive, it is called latent; when active, it is called kinetic. It is held that the same amount of kinetic muscular energy will produce the same amount of motion, and the same amount of motion will produce the same amount of heat. That is, muscular energy, motion, and heat are considered to be equivalents. In the same way other forms of physical force have their equivalents in each other. It is held in physics that whenever one form of physical force ceases to exist, its equivalent is produced in some other form, and that the physical forces generally succeed each other in conformity to this law of force-equivalents. The same principle may be found in mental energy, with laws analogous to the laws of physical forces.

2. But the absolute correlation is only theoretical. The muscular energy can not all be changed to motion. Some of it will be lost in heat. The part which is thus lost, is said to be degraded in form.

LAW I. ONE FORM OF KINETIC MENTAL ENERGY HAS ITS EQUIVALENT IN OTHER FORMS.

First Proof.-This must follow from the third Law of Native Activity. If mental energy may be so directed as to cease acting in one form and made to act in some other form, correlation must be inferred.

Second Proof-The illustrations of the Law are as clearly demonstrative in mental energy as in physical force. Take perception and memory. So long as energy is concentrated upon perception, memory is inactive. In observing facts or listening to an address, some of the energy must be directed to storing away our thoughts in memory or they will soon slip from us. The effort of retention being the same, memory will be strong in proportion to the vividness of perception, the activity of perception contributing to the retentive power. If we compare any intellectual act, as perception or reasoning, with emotion, we shall find that so long as the attention is confined to the intellectual act emotion remains latent. But when perception or reasoning becomes easy, the energy of intellectual activity diminishes and the consciousness of beauty or other feeling is excited. Those who criticise art intellectually are in danger of losing the pleasurable sense of beauty; those who do not lay the foundations of their enjoyment of art in an intellectual discrimination can not appreciate it in a high sense.

OBSERVATIONS.

(I.) As a rider arouses activity in his steed to be used in leaping a hedge by running him on level ground, so the mind is carried over difficult trains of thought by an accumulation of force excited by easier exercises. Thought