26 But when I hear the soul spoken of as something extraordinary, as akin and very near to God, and as coming hither knowing all about past times, I would have it teach, not learn; and not go back to the rudiments, as the saying is, after being advanced in knowledge, but hold fast the truths it has learned when it enters its earthly body. For unless it were so, how could it be discerned whether the soul recalls to memory or learns for the first time that which it hears; seeing that it is much easier to believe that it learns what it is unacquainted with, than that it has forgot what it knew but a little before, and that its power of recalling former things is lost through the interposition of the body?
And what becomes of the doctrine that souls, being bodiless, do not have substance? For that which is not connected with any bodily form is not hampered by the opposition of another, nor can anything be led to destroy that which cannot be touched by what is set against it. For as a proportion established in bodies remains unaffected and secure, though it be lost to sight in a thousand cases; so must souls, if they are not material, as is asserted, retain their knowledge of the past, however thoroughly they may have been enclosed in bodies. Moreover, the same reasoning not only shows that they are not incorporeal, but deprives them of all immortality even, and refers them to the limits within which life is usually closed.
For whatever is led by some inducement to change and alter itself, so that it cannot retain its natural state, must of necessity be considered essentially passive. But that which is liable and exposed to suffering, is declared to be corruptible by that very capacity of suffering.
Source: Against the Heathen (New Advent)