Suppose a new-born mind, entirely blank and waiting for experience to begin. Suppose that it begins in the form of a visual impression (whether faint or vivid is immaterial) of a lighted candle against a dark background, and nothing else, so that whilst this image lasts it constitutes the entire universe known to the mind in question. Suppose, moreover (to simplify the hypothesis), that the candle is only imaginary, and that no 'original' of it is recognized by us psychologists outside. Will this hallucinatory candle be believed in, will it have a real existence for the mind?
What possible sense (for that mind) would a suspicion have that the candle was not real? What would doubt or disbelief of it imply? When we, the onlooking psychologists, say the candle is unreal, we mean something quite definite, viz., that there is a world known to us which is real, and to which we perceive that the candle does not belong; it belongs exclusively to that individual mind, has no status anywhere else, etc. It exists, to be sure, in a fashion, for it forms the content of that mind's hallucination; but the hallucination itself, though unquestionably it is a sort of existing fact, has no knowledge of other facts; and since those other facts are the realities par excellence for us, and the only things we believe in, the candle is simply outside of our reality and belief altogether.
By the hypothesis, however, the mind which sees the candle can spin no such considerations as these about it, for of other facts, actual or possible, it has no inkling whatever. That candle is its all, its absolute. Its entire faculty of attention is absorbed by it. It is, it is that; it is there; no other possible candle, or quality of this candle, no other possible place, or possible object in the place, no alternative, in short, suggests itself as even conceivable; so how can the mind help believing the candle real? The supposition that it might possibly not do so is, under the supposed conditions, unintelligible.[293]
This is what Spinoza long ago announced:
"Let us conceive a boy," he said, "imagining to himself a horse, and taking note of nothing else. As this imagination involves the existence of the horse, and the boy has no perception which annuls its existence, he will necessarily contemplate the horse as present, nor will he be able to doubt of its existence, however little certain of it he may be. I deny that a man in so far as he imagines [percipit] affirms nothing. For what is it to imagine a winged horse but to affirm that, the horse [that horse, namely] has wings? For if the mind had nothing before it but the winged horse it would contemplate the same as present, would have no cause to doubt of its existence, nor any power of dissenting from its existence, unless the imagination of the winged horse were joined to an idea which contradicted [tollit] its existence." (Ethics, ii. 49, Scholium.)
The sense that anything we think of is unreal can only come, then, when that thing is contradicted by some other thing of which we think. Any object which remains uncontradicted is ipso facto believed and posited as absolute reality.
Now, how comes it that one thing thought of can be contradicted by another? It cannot unless it begins the quarrel by saying something inadmissible about that other. Take the mind with the candle, or the boy with the horse. If either of them say, 'That candle or that horse, even when I don't see it, exists in the outer world,' he pushes into 'the outer world' an object which may be incompatible with everything which he otherwise knows of that world. If so, he must take his choice of which to hold by, the present perceptions or the other knowledge of the world. If he holds to the other knowledge, the present perceptions are contradicted, so far as their relation to that world goes. Candle and horse, whatever they may be, are not existents in outward space. They are existents, of course; they are mental objects; mental objects have existence as mental objects. But they are situated in their own spaces, the space in which they severally appear, and neither of those spaces is the space in which the realities called 'the outer world' exist.
Take again the horse with wings. If I merely dream of a horse with wings, my horse interferes with nothing else and has not to be contradicted. That horse, its wings, and its place, are all equally real. That horse exists no otherwise than as winged, and is moreover really there, for that place exists no otherwise than as the place of that horse, and claims as yet no connection with the other places of the world. But if with this horse I make an inroad into the world otherwise known, and say, for example, 'That is my old mare Maggie, having grown a pair of wings where she stands in her stall,' the whole case is altered; for now the horse and place are identified with a horse and place otherwise known, and what is known of the latter objects is incompatible with what is perceived with the former. 'Maggie in her stall with wings! Never!' The wings are unreal, then, visionary. I have dreamed a lie about Maggie in her stall.
The reader will recognize in these two cases the two sorts of judgment called in the logic-books existential and attributive respectively. The candle exists as an outer reality' is an existential, 'My Maggie has got a pair of wings' is an attributive, proposition;[294] and it follows from what was first said that all propositions, whether attributive or existential, are believed through the very fact of being conceived, unless they clash with other propositions believed, at the same time, by affirming that their terms are the same with the terms of these other propositions. A dream-candle has existence, true enough; but not the same existence (existence for itself, namely, or extra mentem meam) which the candles of waking perception have. A dream-horse has wings; but then neither horse nor wings are the same with any horses or wings known to memory. That we can at any moment think of the same thing which at any former moment we thought of is the ultimate law of our intellectual constitution. But when we now think of it incompatibly with our other ways of thinking it, then we must choose which way to stand by, for we cannot continue to think in two contradictory ways at once. The whole distinction of real and unreal, the whole psychology of belief, disbelief, and doubt, is thus grounded on two mental facts—first, that we are liable to think differently of the same; and second, that when we have done so, we can choose which way of thinking to adhere to and which to disregard.
The subjects adhered to become real subjects, the attributes adhered to real attributes, the existence adhered to real existence; whilst the subjects disregarded become imaginary subjects, the attributes disregarded erroneous attributes, and the existence disregarded an existence in no man's land, in the limbo 'where footless fancies dwell.' The real things are, in M. Taine's terminology, the reductives of the things judged unreal.