But, suppose the sphere in which we are placed is filled with an intense, pure, white light, and the objects have no power to analyze it, or suppose the light were red or blue, and so could not be analyzed, and so intense that there could be no difference in shade, it would be the same to us as perfect darkness or the entire absence of light. And, of course, the effect would be the same so far as the distinguishing of objects is concerned, if objects themselves could not analyze, absorb or reflect light. They would be all of one color, or no color, and of the same shade, and as invisible as in the most intense darkness. Hence, to be seen, there must be either two objects, or two parts of the same object, each part of a different color or shade of color. If there is but one object, no object can be seen, even though that object be ourself. Nothing will be seen, no act of perception can take place.

LECTURE V.

FALSE PERCEPTION AND IMAGINATION.

In the preceding Lecture, I have spoken of perception as it takes place when the organs of sense are healthy and act in their normal condition. But it is manifest that if the organs are not in health, or acting in their normal condition, we shall have some form of imperfect act which we call false perception; and we shall best accomplish our purpose of examining and explaining imagination by first considering the forms and conditions. of false perception.

are.

1. Perception, True and False.

We call that true perception, in which we see things as they Or, if one objects to this definition, as assuming improperly a doctrine of ontology, we may accomplish all the object of the definition, by saying that that which we call true perception is that in which any one individual sees objects as they appear to, and are believed to exist by mankind generally; while that would be a false perception in which the object should appear to any one as it does not appear to others generally, and who, for the reason that they are the majority, and agree among themselves in this respect, are assumed to be right. Thus, if one man should see a white object to be red, or see an object

where others, similarly situated, could see none, we should call the act a false perception.

Nobody can tell precisely what is the effect produced in the sensorium by any object acting upon it through the external organs of sense; nor yet can we explain the nature of the act of perception, or show how the mind acts in perceiving. But when the effect is produced in the sensorium, the act of perception takes place and is determined by it. I have spoken of this act as involuntary. We cannot prevent it; we cannot control it. We can turn the eye from an object, and thus avoid seeing it. But if the eye be directed to the object, we cannot but see it. We can give it more or less of our attention. But see it we must. Nor is that all; we must see it according to the sensation it has produced. No effort of our own can change its appearance, as from one color to another, or one form to another. We can, indeed, change its position and so its apparent form, or the medium through which we see it, and thus its apparent color. But the change in both cases is produced by a voluntary act, changing the relations of the object to the organs of sense, and not by any voluntary control over the act of perception.

2. Perception not Voluntary.

This fact is of considerable importance; for upon it depends the certainty of our knowledge. If we could see things as we might happen to choose to see them, rather than as we must, no two persons would see them alike. Nor would the same object appear alike to the same person at different times and under different circumstances. In fact, if we had voluntary control of the act of perception, recognition, or the act of seeing an object the second time, and knowing it to be the same that we saw before, would be impossible. But perception although involuntary, is nevertheless an act, and not an effect merely. It is an act of the mind, and is denoted in all lan

guages by a transitive verb. We ascribe it to ourselves as the agent. We say "I perceive;" whereas we ascribe the sensation to something external to ourselves- we speak of it as an effect produced in us, and not as an act performed by us.

Nor is this all. I have repeatedly said that it is impossible to send any current down the afferent or up the efferent nerves. From this it results that all sensations must not only be involuntary, but they must be produced by something external to, and different from the nerve itself, except in cases of diseased action of the nerve tissues. It seems to be well established that the effect or condition produced in any nerve-centre, is the same in kind, when produced voluntarily by the mind or soul, sending its influence down to the ganglion, so far as this act of sending it down can be performed, as that which is produced by an external object, passing up the afferent, or sensory, nerves to the centre. A jerk of the arm produced by an electric shock, implies the same state of the ganglionic mass in which the nerves of the arm originate, as that which precedes and causes the jerk, when that jerk is produced voluntarily by the mind acting as will. Hence, if we could send any current, effect, or influence down the afferent nerves to the organs in which they terminate, that is, if we could produce sensations ourselves as voluntarily, sensation would be no means of proving the existence of external objects. Nor could it be any sure means of knowledge concerning them.

It will be readily believed, however, from what has been said that if any of the nerve tissues on which sensation depends are diseased, or in any abnormal condition, false perception will be the result. Such abnormal conditions are by no means uncommon. Most persons when suffering from colds, headache, weakness, exhaustion, or other cause of debility, have what is called a "ringing in the ears "—a sensation produced by no outward object, but rather by something in the nerve or surrounding tissues. So with the optic nerve; persons often have what is called "muscæ volitantes," or the appearance of little black specs, as flies, floating before the eyes.

3. In What Sense False, and in What True.

Now these phenomena, considered as sensations are undoubtedly real. And as sensations too, they belong to the class that are matters of consciousness. It is not the sensations, of which we are conscious that are false or unreal, but it is the inference that we draw from them that is unreal; it is the perception that is false. We perceive nothing, for there is nothing to perceive.

And yet in a certain very important sense the perception itself is real. As a mental act it takes place. It is false only in its object. In consequence of the habit we have acquired, and acquired too in our infancy, "whereof the memory of man runeth not to the contrary," so early was it, of referring all perceived objects to a sphere external to ourselves, we do the same thing here when conditions which are similar-but not precisely the same--occur.

I refer to what was said in the last Lecture about our learning the outwardness of objects first from touch and afterwards from sight, and the other special senses.

The perception then is real as a mental act-real as a matter of consciousness, and false only in regard to the objectivity of its object. And it deserves to be specially noted, I think, that in all such cases, where there is not actual insanity involved, there is, whenever the attentiou is called to it, a sense, or consciousness of uneasiness or pain in the organ-eye or ear- - by which the false perception occurs.

4. False Perception Occasioned by the Organs of Sense.

Any distortion, or disturbance, of the organ of sensation, will produce a false perception. Thus, if one of the eyes, for example, be pushed out of place by pressure on the side of it, we see two objects instead of one, for every one that is before the eyes. If we cross the fore finger over the one next to it,