f others of which we are about to speak, so
that the essence of the problems may be understood, is this: that human
knowledge is of two kinds. One is the knowledge of things perceptible to
the senses--that is to say, things which the eye, or ear, or smell, or
taste, or touch can perceive, which are called objective or sensible. So
the sun, because it can be seen, is said to be objective; and in the same
way sounds are sensible because the ear hears them; perfumes are sensible
because they can be inhaled and the sense of smell perceives them; foods
are sensible because the palate perceives their sweetness, sourness or
saltness; heat and cold are sensible because the feelings perceive them.
These are said to be sensible realities.

The other kind of human knowledge is intellectual--that is to say, it is a
reality of the intellect; it has no outward form and no place and is not
perceptible to the senses. For example, the power of intellect is not
sensible; none of the inner qualities of man is a sensible thing; on the
contrary, they are intellectual realities. So love is a mental reality and
not sensible; for this reality the ear does not hear, the eye does not
see, the smell does not perceive, the taste does not discern, the touch
does not feel. Even ethereal matter, the forces of which are said in
physics to be heat, light, electricity and magnetism, is an intellectual
reality, and is not sensible. In the same way, nature, also, in its
essence is an intellectual reality and is not sensible; the human spirit
is an intellectual, not sensible reality. In explaining these intellectual
realities, one is obliged to express them by sensible figures because in
exterior existence there is nothing that is not material. Therefore, to
explain the reality of the spirit--its condition, its station--one is
obliged to give explanations under the forms of sensible things because in
the external world all that exists is sensible. For example, grief and
happiness are intellectual things; when you wish to express those
spiritual qualities you say: "My heart is oppressed; my heart is dilated,"
though the heart of man is neither oppressed nor dilated. This is an
intellectual or spiritual state, to explain which you are obliged to have
recourse to sensible figures. Another example: you say, "such an
individual made great progress," though he is remaining in the same place;
or again, "such a one's position was exalted," although, like everyone
e