We perceive by means of sensations; but our perceptions are not sensations, and sensations are not perceptions. The relation of sensations to perceptions is that of conditionality, or means to an end. Sensation is the condition or means, perception the end. Sensations are not only the constant means of perception in the present life; they are indispensable to this end, and in all conceivable states of being, analogous states of mind must intervene between perceptions and external objects. Disembodied spirits must have capacities analogous to those of sensation, in order to have powers of perception analogous to those which we have here. Perception is in its nature impossible except by means of sensations or other equivalent mental exercises.

§ 14. Sensations are the substratum on which the whole superstructure of ideas rests. They are the fundamental series of mental phenomena, from which all others take their rise, and on which all others are conditioned. The philosophy of sensations therefore ought to be well understood preparatory to the study of other mental exercises. With our present constitution we never could have got the first idea without sensations. These are the starting point of reason and the essential condition of all that depends on reason. After having prosecuted our career for a time with success, and stored our minds with ideas, if all powers of sensation were taken from us, so that we could neither see, nor hear, nor taste, nor smell, nor feel, what would be our condition? What would be the effect of such a deprivation on the powers of thought? It would virtually annihilate them, and result in our consignment to profound repose, from which there would be no possibility of awaking till some sense was restored and operated upon.

Sensations are a wonderful expedient for the development of ideas, and sustain similar relations to the ideality both of animals and men. The lowest grades of animals, and men of the highest orders of intellect and affections, are alike indebted to sensations as the conditions of all their intel lectual and moral attainments. God doubtless might have created us capable of the exercise of reason by other means, and he may furnish us with other analogous endowments to supersede the necessity of these in a future disembodied state; but in the present life, sensation is indispensable to ideality.

15. Every class of sensations answers some useful purpose. None can be spared without injury. Sight, hearing, touch, taste, smell, pain, pleasure, all have their uses, and when properly exercised, subserve our general good. We often complain of pain; the exercise of other senses is in many cases a temporary evil; but how immense is the general good of possessing these capacities under the laws and restrictions which the Creator has put upon them! How irreparable the injury of losing any one of them!

§ 16. The office of sensations as means of perceiving external objects, is perhaps their main office. But the purpose which they answer as pleasures and pains, in exciting desires, giving birth to affections and appetites, and moulding to a great extent the entire character, is of the utmost dignity and importance. The pleasures and pains of sense are of inferior rank to those of the emotions; but they are pleasures and pains. In their place they answer valuable purposes, and are legitimate motives to action. The pains of sense are to be avoided where they consistently can, and sensible pleasures may be lawfully enjoyed.

The pleasures and pains of sense are given us, however, not to be pursued or shunned as ultimate ends of human action, but in subordination to higher ends. Thus the pains of hunger and the pleasures of eating when hungry, are subservient to the due nourishment of the body with food, and to the preservation of life and health. All sensible pains and pleasures subserve similar purposes, which could not be as well secured by other means.

§ 17. Our capacities of sensible pleasure and pain are not of a fixed, unalterable nature, but are generally modified by use. They are strengthened by appropriate exercise, and weakened by being long without exercise. Within certain limits, the more they are exercised, the greater their susceptibilities become; and within other limits, on the opposite scale, the less they are exercised, the weaker they become, till they are reduced to nothing. God has given us these capacities with degrees of susceptibility, and subject to laws of variation perfectly suited to our condition, and adapted in the highest degree to subserve our real good; but at the same time liable to be impaired and rendered excessively sensitive, or morbidly insensible, by improper use.

It is our duty as rational beings to acquaint ourselves with

this part of our constitution, to study the laws of its development, and its uses, and to exercise it in such a manner as will subserve in the greatest possible degree our usefulness and happiness. The due subordination of sensible pleasures and pains, is not an impossibility, or a work of any great difficulty, if it is steadily and resolutely pursued.

§ 18. The power of increasing our capacities of sensible pleasure by exercise, and of diminishing them by disuse, is of great importance. It enables us to modify our constitutional susceptibilities, so as to adapt them to our peculiar circumstances and conditions; and tends, in all conditions and stages of life, to give those capacities of sensation, which are most useful, the greatest susceptibility. The judicious exercise of this modifying power requires sound discretion. Negligence and indiscretion in single instances are often of the greatest injury; when frequent or habitual, they are ruinous and often fatal. Our moral responsibilities extend to the use which we make of our capacities of sensations. The rewards of well doing in the exercise of these capacities, consist, to some extent, in the benefits which flow directly from it, and the punishments of evil doing, in the injuries which we consequently suffer. Not our sensations in particular cases only, but our constitutions as beings capable of sensible pleasure and pain, are to a considerable extent in our own hands, to be moulded and and fashioned according to our choice. This moulding and fashioning power is lodged in our hands for useful purposes, and is, if rightly used, greatly for our advantage. By improper use, that which is given us for good purposes, is made evil; and that which was bestowed as a blessing, is made a curse. The same controlling power by which wise and good men modify their constitutional susceptibilities, so as to adapt them most perfectly to their peculiar circumstances and conditions, is perverted by the unwise and the wicked so as to produce directly contrary results.

19. The dependence of sensations on bodily organs and organic impressions, shows that these faculties are not necessary susceptibilities of minds, but special endowments dependent on appropriate conditions, and capable of being given or withheld at the pleasure of the Creator. Minds might exist and be the same substances which they now are, without sensations in actual exercise and without a capacity to exercise them. The relation between appropriate

organic conditions and the sensations which they occasion, is one of causality and dependence, of which no account can be given except, that such is the will and ordinance of God.

Considered merely in respect to sensations, man does not differ essentially from animals. Many of them are his equals, and in some respects his superiors, considered merely as creatures of sense. The great superiority of man to animals, depends upon the superiority of other human faculties, particularly that of reason.

CHAPTER II.

SENSATIONS SUBSERVIENT TO A KNOWLEDGE OF THE CONDITION OF THE BODY.

Hunger and Thirst.

20. SENSATIONS of hunger and thirst are among the earliest which occur in the experience of sentient beings. The infant gives evidence of being the subject of these sensations, soon after it is born; and men continue to experience them in all the subsequent stages of life. The organ of hunger and thirst is the stomach; and the condition on which these sensations depend in a state of health, is the Iwant of food and drink. Whenever a healthy stomach is empty, and demands food and drink, hunger and thirst are experienced. As soon as proper supplies of food and drink are received, these sensations cease, and recur again when other supplies are required

Hunger and thirst are organic affections of the mind dependent on pecular, conditions of the stomach. The stomach is the instrument only, and the mind the sole agent. In certain forms of disease, the capacities of hunger and thirst are essentially impaired, or entirely destroyed; in others they have an excessive susceptibility, and lead to desires for food and drink, which it is impossible to satisfy, and injurious and often fatal to indulge.

§ 21. Hunger and thirst are a species of pains, and are never agreeable, but always disagreeable. They are a class of natural evils to which we are subjected as an indispen

sable condition to the attainment of the most important benefits. Hunger admonishes us of the want of food; thirst, of the want of drink. When these wants are slight, hunger and thirst are slight; and when they are urgent, hunger and thirst are proportionably intense and distressing. Capacities of hunger and thirst belong in common to men and animals, and are necessary to both. No race of living beings constituted in other respects as men and animals are, could long live without them.

Weariness and Fatigue.

§ 22. Weariness and fatigue are sensations which arise from inaction and labor. Continued inaction produces weariness; and continued labor, fatigue. Weariness and fatigue, in their turn, become the causes of other effects, and produce corresponding desires. Weariness produces desires of action; and fatigue, of rest. These desires are prompted by the painful nature of their exciting sensations, and are directed to labor and rest as means of relief.

Weariness and fatigue may be felt in all parts of the body, and in some parts exclusive of others; and one limb may be the subject of weariness, at the same time that another is affected with fatigue. We may also experience fatigue from reading, speaking, observing natural scenery, pictures, and curiosities of all kinds, and from every variety of studies and intellectual exercises. The Mathematician and Philosopher, the Poet, Novelist, and Divine, are all subject to fatigue in the prosecution of their respective pursuits.

Those most accustomed to labor, are least subject to fatigue from a given amount of exercise; and those most accustomed to inaction, are least subject to weariness from rest. Habitual activity diminishes our susceptibility of fatigue, just in proportion as it increases our capacities for exertion; and habitual inaction diminishes our susceptibility of weariness, just in proportion as it increases our powers of enduring inaction without injury.

§ 23. Weariness and fatigue answer most important purposes in the economy of life; and stand as watchful sentinels to guard us from harm. They operate as regulators of our action and rest, to hold us back when we would venture farther than is safe, and to urge us on, when we would