For this purpose we have been granted the ability to lift our intellect almost all the way into the light enjoyed by the angels in heaven. This lifting allows us to see what we ought to will and what we ought to do in order to be successful during our time in this world and blessed with happiness after death to eternity. We become successful and blessed if we gain wisdom for ourselves and keep our will obedient to that wisdom. We become unsuccessful and unhappy, however, if we devote our intellect to obeying our will. The reason for this is that from the time we are born, our will has a tendency toward evils of various kinds, including evils that are horrendous. If our will was not restrained by our intellect and instead we let it run free, we would quickly fall into criminal behavior; because of our inborn savage animal nature, for purely selfish reasons we would wipe out and butcher everyone and anyone who failed to show us favor or indulge our lusts.
For another thing, if our intellect were incapable of being perfected on its own and of then perfecting our will, we would not be human at all; we would be animals. If there were no separation between our will and our intellect and if the intellect could not rise above the will, we would be unable either to think or to say what we thought. We would only be able to make noises that expressed our feelings. We would not be able to act in reasonable ways, either; we would act on instinct alone. We would be completely incapable of knowing anything about God or seeing him through what we knew; as a result, we would be unable to form a partnership with him and live forever.
We have thoughts and we will things as if we did so on our own. This feeling that we think and will on our own is what allows for a reciprocal partnership [with the Lord]. No partnership can exist without reciprocation. For example, no partnership would exist between an active element and a responsive element if there were no adaptation or point of contact between them.
God alone is an active force. We allow ourselves to experience that active force and we cooperate with it to all appearances as if we were acting on our own, although inwardly we are actually acting from God.
From the statements just made, if you take them in the right way, you can see what human beings are like. You can see the quality of love the human will has if it is lifted up by means of the intellect; and you can see the quality of love the human will has if it is not lifted up.
from True Christianity, Section 588