Material nature is divided into three qualities: goodness, passion and ignorance. Somebody has developed body in the modes of passion. Somebody has developed body in the modes of ignorance. But the root is the spirit soul. And the finer cover is desire - ego, intelligence, mind. And the gross cover is this body.
So Buddha philosophy simply takes account of this gross body. They do not take account of the mind, because as soon as they go to the platform of mind, then immediately the question will be "Whose mind? Whose intelligence?" Then you have to come to the spirit soul. But the people for whom this Buddha philosophy was preached, they are not very intelligent class of men. Therefore Lord Buddha did not give them the information of the subtle body, or the soul. They are unable. Why they were unable? They were gross materialists.