Some animals, also, (oysters,) possess no power of locomotion, and therefore can possess no sexual intercourse. These cases are perplexing to our modes of theorizing; but we avoid the difficulty by attributing verbally to each animal a double sex, and thus its increase is reconciled to the exigency of our experience in other cases.

§ 10. We discover that some plants blossom without producing fruit, and that others of the same species blossom and also produce fruit. We discover, also, that blossoms which bear fruit, will not fructify when they are secluded from the blossoms that bear no fruit. These facts we reconcile to our experience in other matters, by a theory which attributes sex to plants. The fructiferous blossoms are female, the barren are the male; while a certain farina acts as a seminal agent. This is transported to the female organs by insects, or currents of air; and the gross machinery is completed, and fructification rendered satisfactorily intelligible to us.

§ 11.-A sensible cause is a sensible existence, and produces a sensible effect; but in a theoretical cause, nothing is sensible but the effect.

If we exhaust the air out of a tube, (an ordinary pump,) water will ascend thirty-four feet in the pump. Quicksilver will not rise higher in the pump than thirty inches. These facts are as interesting without a theory as with. Still we desire some theory that shall make the ascent analogous to operations with which we are familiar; hence, we say that the atmosphere presses the fluid, and pushes it up the tube. If the push existed, it would perform the office which we assign to it; therefore, we assume its existence; but after we accumulate all the phenomena to which the theory is applicable, (and they are many,) the push is but the verbal agent, by which we make the phenomena conform to other processes with which we are familiar. A sensible pressure is something in itself. It is a feel; (sometimes a sight and a feel;) but the pressure which the atmosphere exerts on water and quicksilver can be neither seen nor felt. All we see is the ascent of the water and quicksilver.

§ 12.—While we employ verbal causes to account for a sensible effect, the process harmonizes with our experience; but when we employ a verbal cause to produce verbal effects, the process leads us to manifest absurdities. The further we proceed in a catenation of such causes and effects, the more evidently we recede from the realities of nature.

That water will ascend in a vacuum thirty-four feet is attributed theoretically to the weight of the atmosphere. The assumed weight is the verbal cause, and it makes the ascent of the water congruous to our own manual operations, and hence is satisfactory to us. But we proceed further: assuming that the verbal weight of the atmosphere is a reality of the external universe, we deduce from it that a man of ordinary dimensions sustains on his body a pressure of fourteen tons weight of atmosphere. Every instance in which we thus react on verbal causes produces a monster as astounding as the above. The result alone ought to teach us that the process is fallacious; especially as the absurdities which the process creates become more glaring, if possible, the further we proceed with it; hence, by a tacit agreement, philosophers usually refrain from deducing any verbal effects from the ability of man to sustain a weight of fourteen tons.

§ 13.—Inquisition concerning the realities of the external universe is limited to the discoveries of our senses; but verbal inquisition is boundless.

I have probably adduced examples enough to show that before we answer any question, we must determine whether the answer is to be verbal or sensible. If the answer is to be restricted to the realities of the external universe, the answer will be limited by what our senses can discover, and we must announce their information in any words which we deem most likely to designate the sights, sounds, feels, tastes, and smells, to which we refer. But if the answer is to be a theory, we may descend into the centre of the earth, or ascend to the cen`tre of the empyrean; we may talk of what happened before the

flood, and what shall occur after the universal conflagration; we may with Newton crush the earth into a size which shall be less than a nutmeg; or, with Descartes, dilate a wine glass full of air till it shall fill all space. But let no man confound such answers with the realities of the external universe. Ingenious they may be, and they may refer to certain sensible experiments; but beyond the sensible existences to which they refer, they are words; and besides words, they are nothing.

14.-In questions, also, which relate to our internal consciousness, we must discriminate whether the answer is to be a theory, or the revelation of consciousness.

All the remarks which I have made on questions that refer to the external universe, apply equally to questions that relate to the universe within ourselves. In this branch of the subject, an answer may either be theoretical or experimental; and before we answer a question, we must ascertain the kind of answer which is required of us for instance,

"Our soul possesses the power," says Locke, "of exciting motion by thought; but if we inquire how the soul produces such an effect, we are entirely in the dark.”

Motion is produced by thought precisely as I experience when I raise my hand to my head. I may find a difficulty in designating by words what I experience; but my knowledge on the subject is complete, for I know the process itself. Locke, however, wanted some theory that should make the process analogous to some external sensible operation, and hence the difficulty.

§ 15.-Theories are usually derived from our familiar physical operations; hence, we cannot invent satisfactory theories for mental operations;-the two departments of creation not being sufficiently analogous.*

When the ascent of water succeeds a vacuum, we reconcile the ascent to our familiar manual operations, by attributing a

* See ante, §§ 2, 3, and 7.

pressure to the surrounding atmosphere; but we possess no external operation that is analogous to the succession of volition and motion; hence, the difficulty of answering the question of Locke: we possess not the means of inventing a satisfactory theory. Locke evidently attributes the difficulty to a mystery of nature, while it is nothing but the inapplicability to mental phenomena of the verbal process by which we construct theories:-theories are all constructed from our physical experience, but physical experience is not congruous to mental operations.

§ 16.-How does memory perform its operations? Before we answer the question, we should ascertain whether the answer must be a theory or a revelation of nature. If the answer is to be a revelation of nature, the mute developments of our experience yield the only correct answer. Words can refer us to these developments; but the moment they attempt more than such a reference, we are theorizing:—that is, we are probably attempting to make the operations of memory analogous verbally to our manual operations. Locke somewhere speaks of the operations of memory under the half allegory and half theory of a schoolboy with a slate, writing down certain events, and which writing eventually becomes obliterated. Again he speaks of memory as an agent that runs about the brain in search of faded impressions; like a lackey in search of a mislaid umbrella. The analogies are so gross, that they are asserted more as an illustration of memory than as a theory; but they evince the usual unacquaintance with the distinction which exists between an inquiry after a theory, and inquiry after the realities of nature.

But

§ 17.-How are remote objects visible? Just as we discover. This would be deemed a very foolish answer; still, it is the best that can be given, for it refers us to the revelations of experience, which alone can yield us a correct answer. the answer is peculiarly dissatisfactory because the question seeks a theory. When we are satisfied of this fact, the above answer is indeed improper. Lord Monboddo answers the question by saying that the soul leaves the body, and emanates to

the distant object. The contact which is thus verbally produced makes vision analogous to our accustomed manual operations, and hence supplies what we require. The reflection of light, and the camera obscura which is produced by a dissected eye, furnish us with a theory that is more congruous to our accustomed operations than even Lord Monboddo's; hence, vision is now performed by the light which rebounds to our eye from visible objects, and produces on the retina a small miniature of the external object. When we get a distant object thus into the eye, we find but little difficulty in understanding how (according to our own operations) an external and distant object becomes cognizable to our minds.

18.-Want of contact with external objects is, you perceive, the difficulty which must be obviated before seeing can be made congruous to our physical operations. A like difficulty pertains to hearing and smelling, and we vanquish it, as in the case of seeing, by a theory which supplies the contact. The air constitutes a medium through which are floated theoretical atoms of odour, and theoretical appulses of sound, from the objects heard and smelt, to the olfactory and auditory nerves.

§ 19.-The silent revelations of experience can alone teach us the realities of our mental nature.

"Actors," when they either laugh or weep, affect spectators with the sensations which the drama expresses. But by what mechanism do the vibrations of the actor's brain transmit themselves to that of other persons?"

§ 20.-Is the answer to be a theory, or a revelation of nature? We must ascertain before we undertake to answer. To know how in reality an actor affects us, we must resort to our experience. The answer will not be words, but the phenomenon itself. If, however, we desire a theory, we must invent some verbal machinery that will make the operation congruous to our manual operations.

* Theory of agreeable sensations, chap. ix. Anon.