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"Hæcin genere sors esse solet humana, ut quid in quovis genere recte aut cogitari aut effici possit sentiant prius quam perspiciant. Laborem autem haud ita levem illum veriti, qui in eo impendendus erat ut, ideas operatione analytica penitus evolventes, quid tandem velint, aut quænam res agatur, sibi ipsis rationem sufficientem reddant, confusis, aut saltem haud satis explicatis rationibus, ratiocinia, et scientiarum adeo systemata superstruere solent communiter, eoque confidentius, quo ejus quam tractant scientiæ fundamentum solidum magis ignorant." Schmidt-Phiseldek,

Philos. Critica Expositio Systematica, t. i. p. 561.

"Pour systematiser une science, c'est-à-dire, pour ramener une suite de phénomènes à leur principe, à un phénomène élementaire qui engendre successivement tous les autres, il faut saisir leurs rapports, le rapport de génération qui les lie; et pour cela, il est clair qu'il faut commencer par examiner ces différens phénomènes séparément." Cousin, Fragm. Philos. p. 8.

THE sensations which we have through the medium of the senses exist only by the presence of the object, and cease upon its absence; nothing being here meant by the presence of the object, but that position of it with respect to the organ, which is the antecedent of the sensation; or by its absence, but any other position.

It is a known part of our constitution, that when our sensations cease, by the absence of their objects, something remains. After I have seen the sun, and by shutting my eyes see him no longer, I can still think of him. I have still a feeling, the consequence of the sensation, which, though I can distinguish it from the sensation, and treat it as not the sensation, but something different from the sensation, is yet more like the sensation, than any thing else can be; so like, that I call it a copy, an image, of the sensation; sometimes, a representation, or trace, of the sensation.

Another name, by which we denote this trace, this copy, of the sensation, which remains after the sensation ceases, is IDEA. This is a very convenient name, and it is that by which the copies of the sensation thus described will be commonly denominated in the present work. The word IDEA, in this sense, will express no theory whatsoever; nothing but the bare fact, which is indisputable. We have two classes of feelings; one, that which exists when the object of sense is present; another, that which exists after the object of sense has ceased to be present. The one class of feelings I call SENSATIONS; the other class of feelings I call IDEAS.

It is an inconvenience, that the word IDEA is used with great latitude of meaning, both in ordinary, and in philosophical discourse; and it will not be always expedient that I should avoid

using it in senses different from that which I have now assigned. I trust, however, I shall in no case leave it doubtful, in what sense it is to be understood.

The term Sensation has a double meaning. It signifies not only an individual sensation; as when I say, I smell this rose, or I look at my hand: but it also signifies the general faculty of sensation; that is, the complex notion of all the phenomena together, as a part of our nature.

The word Idea has only the meaning which corresponds to the first of those significations; it denotes an individual idea; and we have not a name for that complex notion which embraces, as one whole, all the different phenomena to which the term Idea relates. As we say Sensation, we might say also, Ideation; it would be a very useful word; and there is no objection to it, except the pedantic habit of decrying a new term. Sensation would in that case be the general name for one part of our constitution, Ideation for another.

It is of great importance, before the learner proceeds any farther, that he should not only have an accurate conception of this part of his constitution; but should acquire, by repetition, by complete familiarity, a ready habit of marking those immediate copies of his sensations, and of distinguishing them from every other phenomenon of his mind.

It has been represented, that the sensations of

sight and hearing leave the most vivid traces; in other words, that the ideas corresponding to those sensations, are clearer than others. But what is meant by clearer and more vivid in this case, is not very apparent.

If I have a very clear idea of the colour of the trumpet which I have seen, and a very clear idea of its sound which I have heard, I have no less clear ideas of its shape, and of its size; ideas of the sensations, neither of the eye, nor of the ear.

It is not easy, in a subject like this, to determine what degree of illustration is needful. To those who are in the habit of distinguishing their mental phenomena, the subject will appear too simple to require illustration. To those who are new to this important operation, a greater number of illustrations would be useful, than I shall deem it advisable to present.

It is necessary to take notice, that, as each of our senses has its separate class of sensations, so each has its separate class of ideas. We have ideas of Sight, ideas of Touch, ideas of Hearing, ideas of Taste, and ideas of Smell.

1. By Sight, as we have sensations of red, yellow, blue, &c., and of the innumerable modifications of them, so have we ideas of those colours. We can think of those colours in the dark; that is, we have a feeling or consciousness, which is not the same with the sensation, but which we contemplate as a copy of the sensation, an image of

it; something more like it, than any thing else can be; something which remains with us, after the sensation is gone, and which, in the train of thought, we can use as its representative.

2. The sensations of Touch, according to the limitation under which they should be understood, are not greatly varied. The gentle feeling, which we derive from the mere contact of an object, when we consider it apart from the feeling of resistance, and apart from the sensation of heat or cold, is not very different, as derived from different objects. The idea of this tactual feeling, therefore, is not vivid, nor susceptible of many modifications. On the other hand, our ideas of heat and cold, the feelings which we call the thought of them, existing when the sensations no longer exist, are among the most distinct of the feelings which we distinguish by the name of ideas.

3. I hear the Sound of thunder; and I can think of it after it is gone. This feeling, the representative of the mere sound, this thinking, or having the thought of the sound, this state of consciousness, is the idea. The hearing of the sound is the primary state of consciousness; the idea of the sound is the secondary state of consciousness; which exists only when the first has previously existed.

The number of sounds, of which we can have distinct ideas, as well as distinct sensations, is

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