Though so much interested in acquiring a thorough knowledge of ourselves, yet I do not know if man is not less acquainted with the human, than with any other existence. Provided by nature with organs, calculated solely for our preservation, we only employ them to receive foreign impressions. Intent on multiplying the functions of our senses, and on enlarging the external bounds of our being, we rarely make use of that internal sense which reduces us to our true dimensions, and abstracts us from every other part of the creation. It is, however, by a cultivation of this sense alone that we can form a proper judgment of ourselves. But how shall we give it its full activity and extent? How shall the soul, in which it resides, be disengaged from all the illusions of the mind? We have lost the habit of employing this sense; it has remained inactive amidst the tumult of our corporeal sensations, and dried up by the heat of our passions; the heart, the mind, the senses, have all co-operated against it. Unalterable in its substance, and invulnerable by its essence, it still, however, continues the same. Its splendor has been overcast, but its power has not been diminished: it may be less luminous, but its guidance is not the less certain. Let us then collect those rays, of which we are not yet deprived, and its obscurity will decrease; and though the road may not in every part be equally filled with light, we yet shall have a torch that will prevent us from going astray. The first and most difficult step which leads to the knowledge of ourselves, is a distinct conception of the two substances that constitute our being. To say simply, that the one is unextended, immaterial, and immortal, and that the other is extended, material, and mortal, is only to deny to the one, what we affirm the other possesses. What knowledge is to be acquired from this mode of negation? Such negative expressions can exhibit no positive ideas: but to say that we are certain of the existence of the former, and that of the latter is less evident; that the substance of the one is simple, indivisible, and has no form, since it only manifests itself by a single modification, which is thought; that the other is a less substance than a subject, capable of receiving different forms, which bear a relation to our senses, but are all as uncertain and variable as the organs themselves; that is to say something; it is to ascribe to each such distinct and positive properties as may lead us to an elemental knowledge of both, and to a comparison between them.