The faculty of perceiving the objects which surround us, is an important feature in the history of mind; but by what means or contrivance this is effected, can only be known to the Supreme Being, who has thus been pleased to endow us; and our utmost endeavours to detect the modus operandi will be puerile and unavailing.

The first operations of the infant are to educate its senses, in order to become acquainted, through these organs, with surrounding objects. This, in the human species, is a process of very slow attainment; and our information concerning this subject, must be derived from attentively watching the progress of the infant itself; as of these early perceptions, for a reason which will be afterwards assigned, we retain no distinct recollection.

For the manner in which we become acquainted with the objects in nature, we have appropriated a term, which was probably supposed to be explanatory of the process, by which we received our intelligence of these phenomena, and have accordingly termed it Perception. The intrinsic meaning of this word is the taking, seizing, or grasping, of an object, from the Latin Cum and Capio, and the same figure pervades most of the European languages. This term may sufficiently apply to the information we derive from the organ of touch; but it affords no solution of that which we obtain through the medium of the other senses, as sight, smell, and hearing. It has been the bane of philosophy, and the great obstacle to its advancement, that we have endeavoured to penetrate that which is inscrutable; and in this vain pursuit, we have neglected to detect and cultivate that which is obvious, and the legitimate province of our research.

These organs of sense are the instruments by which we obtain our different perceptions; they are the tests by which we become acquainted with the objects of nature.

When we view the newly-born infant, and consider its state for many weeks after it has become a member of our community, we are then enabled to form some opinion of the almost insensible gradations, by which it acquires its perceptions. An enumeration of the progressive steps of this tardy process is within the power of any patient and accurate observer; but this detail does not constitute a part of the plan which has been adopted.

It has been endeavoured by writers on this subject, to establish a distinction between perception and sensation, and the reader for his information may consult their works: they do not however appear to have founded this distinction on any obvious difference, nor to have adduced sufficient reasons for their separate establishment, as independent properties of the nerves. To feel, to experience a sensation, or to perceive, implies consciousness; it is that which is transmitted by the nerves to the sensorium, either by the organs of sense, or by the internal nerves; as pain, or feelings of which we are conscious. Consciousness is the test, the evidence, the proof of sensation or perception. This point has been adverted to, in order that terms should not be multiplied without a distinct and essential difference of meaning.

The five senses, together with some auxiliaries, which will be the subjects of future notice, may be considered as the instruments or agents, by which the edifice of mind is constructed. In the act of perceiving by the different senses, there are some circumstances, which are particularly deserving of attention. In order that perception may fully and certainly take place, it is necessary that the person should be undisturbed; he ought to be exempt from external intrusions, and internal perturbation. During this process the respiration is in general more slowly drawn, the body endeavours to maintain a perfect quietude, and its position becomes fixed. When we perceive objects by the eye, this organ becomes fixed and the lips are usually closed. During our examinations by the touch, the eye is also fixed, the breathing is suspended, and the lips brought into contact: the fingers are separated, and their more delicately tangent surfaces applied to the object with their utmost expansion. In the exercise of audible perception, the neck is stretched forth, and the ear applied to the quarter from whence the sound appears to issue; the mouth is partly open to conduct the vibrations to the Eustachian tube. When we acquire intelligence by the smell, the lips are very firmly closed, the nostrils become dilated, and the inspiration of air through them is conducted by short and successive inhalations. From the connection between the smell and organs of taste, (and this association is more remarkable in some animals than in man,) it is difficult to describe the process, which, however, principally consists, when minutely tasting, in moving the tongue (the principal discriminator) on the palate:—but when urged by strong appetite as in the act of feeding, and when divested of the restraints which refined society imposes; the nostrils are widely expanded, the eye is keenly directed to the portion, and the hands are busily employed.

Experience has sufficiently informed us that the organs of sense must be in a healthy state, in order to the due conveyance of perception. When the function of any organ is altogether defective, as when a person is born blind, he is cut off from all perception of light and of visible objects. If by nature deaf, from the intonation of sounds; and many unhappy instances of such connate defects abound among our species. In one particular subject, both these defects existed from birth; so that the sum of his intelligence was conveyed by the touch, smell, and taste, or in other words, his mind was exclusively composed of the perceptions he derived from these senses. This case will be more particularly noticed in a subsequent chapter. The alterations which take place in the state of our perceptions from a morbid cause, are generally known. Thus a person labouring under a catarrh, will be unable to detect the odours which certain substances communicate in a healthy condition of his olfactory organ. In fever excited by a disordered stomach, the taste will become vitiated, and the partial obstruction of the ear by accumulated wax, will impress him with the bubbling of a pot, the singing of birds, or the ringing of bells.

The same law that produces fatigue in a muscle from exertion, appears to obtain in the organs of sense. If they be excited by their appropriate stimuli too violently, or for a too long continuance, fatigue or languor is produced, their percipience is diminished, or confusedly conveyed; and they require a period of rest for their refreshment.

As we advance in our enquiries into the nature of perception, it will be evident that we cannot long continue to treat of it as a simple act, or as a distinct faculty. The organs by which we obtain our different perceptions are not insulated parts, but communicate with a substance, termed the brain, and which is continued through the vertebral column. The ultimate expansion of a nerve of sense, has been termed its sentient or percipient extremity; and where it is united to the brain, its sensorial insertion. If we were to divide the optic nerve where it passes into the foramen, taking care to leave the apparatus of the eye uninjured, the visual organ would be deprived of its function, and the person or animal would be completely blind of that eye; so that a communication with the brain is necessary for the purpose or act of perception. As therefore the union of the nerve with the brain is indispensably necessary for the purpose or act of perception, we are naturally led to inquire into the properties of this substance, termed the brain. Before we proceed to this part of the subject, it will be proper to notice a fact which is of frequent occurrence. In amputations of the thigh, at the moment the femoral nerve is divided, it often occurs that a pain is distinctly felt in the toes; and after the limb has been removed, even for many months, the same painful feeling of these lost extremities is occasionally experienced. This circumstance would render it probable that the larger branch of the nerve becomes itself impregnated with the sensation it transmits: indeed it is a continuation of the same substance, from its sentient extremity to its sensorial insertion. This intimate union of nerve and brain may be further illustrated: it has been already noticed, that a morbid state of the organs of sense will convey inaccurate perceptions; and it is equally certain, that disease of the brain, will excite phantasms, which appear as realities to the sensitive organs.As consciousness is implied, in order to constitute the act of perception, it is of some importance to investigate the nature and meaning of this term. The consciousness of having experienced a perception by any of the senses would be an act of memory: consciousness, therefore, applies to the past; and it also accompanies our prediction of the future. When a person is writing a letter, he is at the time, conscious that his own hand is forming the characters; if this letter be afterwards submitted to his inspection, he is conscious that he wrote it; and if he be desired to write it over again, he is conscious that it will bear, both to himself and others, the character of his hand-writing. Consciousness, therefore, accompanies human action through all its tenses: it is equivalent to the knowledge we possess of our own personal identity, the evidence of mind, and therefore must accompany every act of intelligence. Thus we are equally conscious that we perceive, remember, think or reflect, and reason. As consciousness must accompany every act of perception, it follows that we cannot be impressed with more than one at the same instant; for it can never be contended that we are able to experience two acts of consciousness at the same moment. The very term two, implies repetition or succession, and we could as well conceive the possibility of being, at the same time, in two different places.

As far as we are warranted to infer from the evidences it affords, an infant appears to possess no consciousness; but it may be considered of early acquirement, and coeval with distinctness of perception.

These few preliminary remarks concerning perception have been submitted to the notice of the reader, in order to advance to another subject. The faculties which constitute mind are so blended, and dependant on each other, that it would only hazard confusion to proceed. But this subject will be resumed.[1]