to involve solidity and the other primary qualities; but the latter class is termed "6 secondary," because they are first perceived simply as powers (resident, of course, in some substance) to produce certain sensations within the soul.

It is true that secondary qualities may often be explained, and may always be accounted for, as immediately resulting from some particular development of the secundo-primary; and cases arise in which powers belonging to these two classes may form a unity and be thought of together and under one conception. For example, hardness and softness, roughness and smoothness, may be regarded both as certain dispositions of the particles of solid bodies, and as the causes of certain sensations in our nervous system.

The distinction, however, between the secundo-primary and the secondary is rightly made, even though it may sometimes call us to discriminate a thing as viewed in one light from itself as viewed in another. It is not weakened, but confirmed, by the analysis of those cases in which the two modes of quality combine; and it is necessary if we would describe and distinguish our conceptions of outer things according to their natural formation in the mind.

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That a reference to solidity qualifies our conception of the secundoprimary characteristics of matter is taught by Hamilton when he says that these qualities are known by pressure; for this is the indication of solidity. His words are: They have all relation to space and to motion in space, and are all contained under the category of resistance or pressure.' We would prefer to say that they all become known to us in connection with pressure and resistance. Moreover, we prefer a different statement from that of Hamilton, when he says that the secundoprimary qualities may be considered in two lights, the objective, or physical, and the subjective, or psychological; the latter referring to the sensations which they are able to cause. Whenever qualities are viewed simply as the causes of sensations, we would consider and call them secondary; but whenever they may be viewed as related to both physical and psychical effects, we would regard them as a combination of the secondary with the secundo-primary. But secundo-primary qualities, per se, seem wholly physical, or objective.

Finally, that peculiar class of qualities which Locke inclines to place with the secondary may better be regarded as secundo-primary qualities perceived and conceived of by means of an external character or relation. Though they refer to psychical results, they immediately relate to the action of matter upon matter.

The secundo

enumerated.

We shall now give Hamilton's account of the secundoprimary primary qualities almost in his own words. His classificaqualities tion of the qualities has reference to the general nature of the forces manifested in them. These are of three kinds, namely, that of co-attraction, that of repulsion, and that of inertia. a. There are two subaltern genera of co-attraction, - to wit, that of gravity, or the co-attraction of the particles of body in general; and that of cohesion, or the co-attraction of the particles of this and that body in particular. Gravity or weight, according to its degree, which is in proportion to the bulk and density of ponderable matter, affords the relative qualities of the heavy and the light. Cohesion, using that

term in its most unexclusive universality, is the basis of many species of qualities. Without proposing an exhaustive list, we enumerate: (1) the hard and the soft; (2) the firm or solid, and the fluid or liquid,

this last being subdivided into the thick and the thin; (3) the viscid and the friable; (4) the tough and the brittle; (5) the rigid and the flexible; (6) the fissile and the infissile; (7) the ductile and the inductile; (8) the retractile, or cohesively elastic, and the irretractile; (9) the rough and the smooth; and (10) the slippery and the tenacious.

b. The force of repulsion is manifested in greater or less degrees of resistance to compression, that is, in (1) relative compressibility and incompressibility; and also in greater or less degrees of resiliency, or the elasticity of repulsion, that is, (2) in resiliency and irresiliency. c. Inertia - or, more fully, the vis inertia is the tendency whereby body continues in a state of rest or of motion till acted upon from without. Combined with bulk and cohesion, it results in the movable and immovable, that is, the easy and the difficult to move.

--

In the foregoing list the powers of chemical combination and of molecular adhesion are omitted, and should perhaps be added to those qualities which are enumerated under the general head of cohesion. The tendency to chemical combination is an important and widely operative attribute of matter; and so, also, is that adhesive force which is exhibited in capillary action, in the solution of a solid in a liquid substance, and in the saturation of one fluid substance by another. Such is the enumeration of Hamilton.

Secondary qualities are

causes con

ceived of by

an external mark.

3. We now pass to the secondary qualities of matter. These may be defined as causes existing in body to produce the various sensations of which man is capable, considered without reference to their own constitution, but simply as the causes of the sensations.

We may be ignorant of the nature of that which produces some sensation in us, while yet we are sure that there is something external to us which has a power to affect us in a given way. Only philosophic research reveals the nature of such things as color, sound, odor, heat, cold, and so forth; but every one knows that things are colored, sonorous, odoriferous, hot, and cold, for these are all the objects of special perceptions.

We cannot approve of the language of Professor Stewart and other authors who speak of secondary qualities as the unknown causes of our sensations; this language is calculated to mislead. Every such quality is known as a cause, and much even may be ascertained of the character of the cause. But it is to be allowed that our conception of the quality does not contain any reference to the particular constitution of the cause, and may be formed and entertained while we are ignorant of that constitution.

That secondary qualities are of the nature of causes is taught by Locke when he says that they are "nothing but powers to produce various sensations in us ;" which doctrine has come down from Aristotle, and accords with the universal belief of men. When men say that fire is hot, and that grass is green, and sugar sweet, and thunder loud, they mean not only that we have given sensations, but that there is a power in certain things to produce these feelings. To ascribe such a

power to any object does not necessarily involve that any soul is or will be actually affected by it, but only that the proper affection can and will be produced whenever the object may be brought to act on the sensorium. There is literal truth in what the poet says:

"Full many a gem of purest ray serene

The dark unfathomed caves of ocean bear:
Full many a flower is born to blush unseen,

And waste its sweetness on the desert air."

Moreover, there is no reason to suppose that the external quality resembles the feeling in the mind, or partakes of its nature. The quality is simply a power in some material substance to cause a peculiar motion in the matter of our nervous system; and even this motion is something wholly different from sensation, the latter being an affection of the mind excited by the nervous action, but deriving its peculiar character from the activity of the mind itself. The perception of the quality takes place when we perceive the sensation as an effect and as determined by some cause not within the soul itself.

These remarks will explain that war of words as to whether heat and cold, colors, sounds, tastes, and smells exist in external objects, or in the mind only, or in both. They plainly reside in both, but in different senses. The sensations of heat and cold, color and taste, are in the mind only; the external causes or conditions of these sensations reside in bodies. It is the part of such sciences as acoustics and optics to ascertain the nature of these causes and the mode of their operation; and modern investigation only confirms the conjecture which Aristotle ascribes to Democritus, that savors, odors, and colors consist in the configuration and action of particles of matter. Summary The views which have now been advocated may be of views. summed up as follows. By the qualities of body philosophers have meant those properties which belong exclusively to matter, or the solid substance. The principal primary qualities are solidity, size, figure, mobility, divisibility, and situation; to which possibly two or three others less noticeable might be added. These are conceived of, not abstractly, but as attributes necessarily, and therefore universally, accompanying solidity.

The secundo-primary qualities are powers which bodies have to act upon one another. They also are immediately perceived, and conceived of, as connected with solidity, yet not necessarily concomitant of it. Only solid bodies are known to attract and repel each other in space, and to resist any change from a state either of rest or of motion. Yet we might conceive matter to exist without any powers of attraction or repulsion or inertia. Science has established that some of the laws according to which matter acts upon matter are very general. The proposition has been ably maintained that gravity and inertia are universal attributes. It is the province of scientific inquiry, not of immediate intuition, to determine such questions and all others relating to the nature and extent of the secundo-primary qualities of body.

Finally, the secondary qualities are powers residing in material things to produce sensations in us. We cannot accept the language of Hamilton when he says: "As we are chiefly concerned with these qualities on their subjective side, I request it may be observed that I shall

employ the expression secondary qualities to denote those phenomenal affections determined in our sentient organism by the agency of external bodies, and not, unless when otherwise stated, the occult powers themselves from which that agency proceeds." Only confusion can result if we identify sense-affecting qualities with the affections which they produce. But we may conceive of powers without reference to the physical conditions out of which they arise. We may do so even while ignorant of the nature of such conditions, the essential or differentiating element in our conception being purely relative, and based on the effect which the power produces; thus we conceive of the secondary qualities of matter.

The real ground of the division of properties, which we have now considered, lies in the different ways in which our perception and conception of solidity-or of extension and solidity, the essential properties of matter

are related to our perception and conception of material properties in general. While all the qualities, according to our ultimate understanding of them, belong exclusively to matter, the primary attributes are perceived, and conceived of, as necessarily belonging to all extended and solid substances; the secundo-primary as belonging only to matter or the solid substance, yet, so far as we can see, contingently; while the secondary qualities are perceived, and conceived of, without any such perception of their relation to an extended solid. From the first they are perceived as powers belonging to a substance other than the soul, and external to it; but it is by subsequent comparison and judgment that they are connected with solidity in the substances which they characterize. Hence our conceptions of them do not ordinarily contain any reference to solidity.

CHAPTER XXXVIII.

CONCOMITANT PERCEPTION.

Concomitant 1. THE distinction between direct and concomitant perception defined and perception has not received the recognition which it established. deserves. Most writers, and in particular those who Locke, and have lived within the last one hundred years, have emReid quoted. braced all our immediate knowledge under the heads of consciousness and sense-perception.

Aristotle,

They have been induced to do so partly because the same discussion applies largely to all our original cognitions, and yet more because our concomitant perceptions are so intermingled and united with those which are more direct, that the former have naturally been treated as subordinate parts of the latter.

This method of treatment has a great disadvantage. It brings the language of philosophy into conflict with that of com

mon speech; it makes philosophy use words wrongly, and teach what is not strictly and literally correct. To say that space is perceived by sense-perception, and duration by consciousness, is to teach what is not true according to our ordinary conception of the operations and objects of these powers; neither can we say that the relations of number or quantity or causation are perceived by these powers, or by either one of them. But we can affirm that space, time, number, quantity, and causation are perceived in connection with the objects both of sense-perception and of consciousness.

a di

The adoption of language other than this has led some to make a division of these common objects so as to assign some of them to sense-perception and some to consciousness, vision arising solely from the assumption that there are only two modes of immediate cognition. The better plan in this case, as in every other in which it can be employed, is to conform the language of philosophy to that of daily life. Following this method, we may hope to obtain more correct apprehensions, both as to our perceptions and as to the objects of our perceptions, than can be obtained in any other way.

Although concomitant perception has not received any formal place in the systems of philosophers, their writings contain intimations which greatly justify its more perfect recognition. Aristotle teaches that there are three kinds of sensibles, or (as the word might be translated) of sense-perceptibles, and that two of these are perceived in themselves (κať avтà), while one is perceived by its accidents (karà σνμßeßηkós). By this last we understand the object of acquired perception, as when, seeing a white thing, we recognize the son of Diares; for to be the son of Diares is something contingent, and not necessary, to the whiteness perceived. About this kind of perceptibles we are sometimes mistaken.

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Of things sensible in themselves, and about which we do not mistake, there are two kinds, -the proper, which belong severally to the several senses; and the common, which belong to all. The common are motion, rest, number, form, and size. But, adds Aristotle, " of things sensible in themselves, the proper are pre-eminently objects of sense perception, and things to which the nature of each sense is adapted ” (“ τῶν δὲ καθ ̓ αὑτὰ αἰσθητῶν, τὰ ἴδια κυρίως ἐστὶν αἰσθητὰ, καὶ πρὸς ἃ ἡ οὐσία πέφυκεν ἑκάστης aioonσews"). Thus he makes the common sensibles to be the objects of sense only in a secondary and improper way. Elsewhere he styles them the concomitants and consequents (akoλovθέντα, επόμενα) of the proper.

Locke, though very inadequately, recognizes concomitant per