§ 104. The following are the most important modes in which the constructive imagination is found to operate:

(1.) In imagination, there may be a separation of the parts or qualities of which any object is made up. We can imagine a horse without its head; a flower without its colour or smell; a bird without its wings; a human being without some quality or character which he now possesses.

(2.) In imagination, parts or qualities thus separated from their natural relations may be recombined so as to form new objects. Centaurs, winged bulls, griffins, &c., are illustrations of this process.

(3.) In this reconstructive process, the elements of the new object may be greatly and variously modified, may be changed in shape, size, or excellence, either for improvement or deterioration. Conformity to the truth of nature is not at all an essential feature of the product of imagination.

(4.) In imagination, when we wish to represent to ourselves something unknown, we can do so only by employing elements taken from things known. We are frequently bound to believe in the existence of things which we have not directly known, and probably can never know. In this case the imagination clothes the unknown with forms taken from the known,

(5.) In the object which the imagination constructs there must be a certain congruity between the elements of which it is made up, in order to render

the imaginative act possible. To imagine a square circle, for example, would be impossible.

CHAP. IV.

SECT. IV.

Imaginascience.

tion in

§ 105. We shall now study the operations of the imagination as they are found in the most important departments of human mental activity,-in science, in art, in ethics, and in religion. It may perhaps be thought somewhat incongruous to unite imagination with science, as science is usually supposed to deal only with known facts. But the truth is that nearly all the great discoveries of science have been the result of an effort of imagination; and many of the greatest men who have advanced scientific knowledge have been men gifted with a strong constructive imagination. Let us study the part which imagination plays in the progress of scientific discovery. Some phenomenon, say the fall of rain from the clouds, requires to be explained. It is observed Illustrated. that dark clouds appear in the sky; the lightning flashes; the thunder rolls; the rain falls in torrents. The cause of all this is unknown, and people set their imagination at work to think of what the cause may be. In other words they frame an hypothesis. Now in all cases, the nature of the hypothesis framed will depend upon the nature and amount of the knowledge or belief possessed by the persons who frame it. The uneducated Hindu peasant sees the dreadful commotion in the skies, and imagines that the elephant of Indra is up there throwing down the water which he has taken from the sea with his trunk. If any difficulty presents itself, it will soon be got over by the reflection that

CHAP. IV.
SECT. IV.

Further described.

Indra is great and can do all things. This is an illustration of a very primitive kind of hypothesis framed for the explanation of phenomena. But as men advance, they observe more closely the phenomena of nature. Vapour is frequently seen rising from the surface of water; especially when heat is applied, this takes place. At length some genius, by an effort of imagination, sees the analogy between the formation of clouds in the heavens and the accumulation of steam in a room in which there is heated water. This observation is a hint which may assist in the formation of a new hypothesis. One hint after another of a similar kind is taken advantage of, until everything connected with the thunderstorm is found to be analogous to some well-known natural operation. Then the mind is satisfied and the hypothesis becomes a theory.

§ 106. The foregoing is an illustration of the manner in which nearly all the most important scientific discoveries have been made. Some great series of natural phenomena requires an explanation. Its cause is unknown, or people are dissatisfied with the explanation hitherto given. The imagination of some Newton is brought to bear upon the problem. His genius enables him to imagine that the unknown cause of the phenonema in question is identical with the cause of some familiar event; he sees an analogy between the phenomena, and he imagines an identity of cause; the result is a new hypothesis. After the formation of the hypothesis, its value requires to be tested by

ascertaining whether it is able to explain all the phenomena.

CHAP. IV.
SECT. IV.

Imagination of hypothetical

§ 107. There are hypothetical explanations of phenomena which can never be the objects of direct observation, and in this case imagination may be occupied in forces. an endeavour to represent them before the mind. The cause of the sensation of light or colour, for example, is, and always must be, hypothetical. The generally accepted hypothesis is that the whole of space is pervaded by a very refined ether, and in that ether vibrations of immense minuteness and rapidity are being perpetually propagated in straight lines from luminous bodies. These vibrations, striking upon the retina of the eye, cause the sensation of light. Now, in this hypothesis the vibration is the essential element; the ether is an hypothetical addition, invented for the purpose of making the imagination of the vibration possible. A vibration with nothing to vibrate is inconceivable; hence it was necessary to invent an hypothetical ether in which the vibration could take place. But in imagination, ether is represented as simply a refined kind of atmosphere; and the vibrations are represented as analogous to what we are able to observe when we look at a distant object through a column of heated air. Thus imagination represents the unknown cause of our visual sensations by analogy from phenomena which we know. We clothe the unknown with forms taken from the known. But it must be remembered that this does not remove the hypothetical character of the explanation. That which, from

CHAP. IV.
SECT. IV.

Imagination in art

Mechani

cal.

its nature, can never be presented to consciousness, can never be truthfully represented in imagination. But yet it is necessary, when we think of hypothetical causes which from their nature are unknown, that we should imagine them as invested with a phenomenal clothing something analogous to what we have known. Such is the limitation of the human

mind.

§ 108. We now proceed to examine the operations of the imagination as found in the production of works of art.

In the ordinary mechanical arts, the chief exercise of the imagination is seen in the skilful adaptation of means to ends. Some work requires to be done; the mechanical genius is able to see what particular means, or what combination of means, will suffice to do the work. The means at hand are, generally speaking, of two kinds; artificial instruments, and natural forces. A great deal of genius has been, at different times, shown in devising plans for connecting the latter with the former, for connecting the natural forces of the world with the artificial instruments of man's construction. The windmill, the water-wheel, the steam-engine, the electrical machine are all illustrations of this connection. And the imagination of mechanical inventors has been chiefly exerted in devising schemes for getting hold of, governing, guiding, or modifying the various forces of nature.

§ 109. In the fine arts, we have a higher, although perhaps not a more useful, exercise of the