It is tremendously difficult to explain comprehensibly what an understanding of truth and a will to do good are, in the strict sense. The reason for the difficulty is that we consider every thought passing through our minds to be part of our intellect (since that is the name we give it) and every desire entering our heart to be part of our will (since that is the name we give it).
What makes a clear explanation even harder is that many people today are also completely unable to tell the difference between activity in the intellect and activity in the will. When they think something, they say they want it, and when they want something, they say they think it. So again the obstacle is the labels people use.
Yet another barrier to comprehension is the fact that only what relates to their body captures people’s interest; that is, their lives are exceedingly shallow.
For all these reasons, people are unaware that each of us has a deeper level inside, and another level deeper than that, and another level that is deepest of all. They do not see that our bodily urges and sense impressions form the outermost surface; our passions and memories, a deeper layer; our loves and rational thoughts, a still deeper layer; and a will to do good and a comprehension of truth, the deepest. These levels are differentiated from one another with the greatest possible clarity. Body-centered people, however, jumble them all together into an undifferentiated whole. This is the source of the belief that when our physical part dies, everything else must too, even though it is at death that we first start to live. Indeed the new life comes to us by way of our inner levels, passing through each level in order.
If our inner dimensions were not clearly distinguished in this way, and if they did not lie one within the other, in the next life we could never become spirits, never become angelic spirits, never become angels. These three groups are differentiated in the same way as the inner levels, which create the plainest demarcation possible among the three heavens.
This explanation casts a little light on what a comprehension of truth and a will to do good are, properly speaking, and shows that they can be ascribed only to a person whose character is heavenly, or to angels in the third heaven.
from Secrets of Heaven, Volume 1, Section 634