Thomas Aquinas

“ I answer that, Some say that the habit of knowledge resides not in the intellect itself, but in the sensitive powers, namely, the imaginative, cogitative, and memorative, and that the intelligible species are not kept in the passive intellect. ”

“ Gregory, on the other hand, is positive, since he says, "We cannot believe." His opinion, indeed, seems to be the more probable one---that the souls of the blessed who see God do know all that passes here. For they are equal to the angels, of whom Augustine says that they know what happens among those living on earth. But as the souls of the blessed are most perfectly united to Divine justice, they do not suffer from sorrow, nor do they interfere in mundane affairs, except in accordance with Divine justice. ”

“ The future, which is distant in time, does not actually exist, and therefore is not knowable in itself, because so far as a thing falls short of being, so far does it fall short of being knowable. But what is locally distant exists actually, and is knowable in itself. ”

“ Neither can the intelligible species in the passive intellect be corrupted by their contrary; for there is no contrary to intelligible "intentions," above all as regards simple intelligence of "what a thing is." But contrariety may exist in the intellect as regards mental composition and division, or also reasoning; so far as what is false in statement or argument is contrary to truth. And thus knowledge may be corrupted by its contrary when a false argument seduces anyone from the knowledge of truth. ”

“ Now it is clear that in the natural order human souls hold the lowest place among intellectual substances. But the perfection of the universe required various grades of being. If, therefore, God had willed souls to understand in the same way as separate substances, it would follow that human knowledge, so far from being perfect, would be confused and general. ”

“ Further, some in this world who are less good enjoy knowledge denied to others who are better. If, therefore, the habit of knowledge remained in the soul after death, it would follow that some who are less good would, even in the future life, excel some who are better ”

“ But separate substances cannot be known to the soul by their presence, for God alone can enter into the soul; nor by means of species abstracted by the soul from an angel, for an angel is more simple than a soul. Therefore the separated soul cannot at all understand separate substances.
Objection 3: Further, some philosophers said that the ultimate happiness of man consists in the knowledge of separate substances. If, therefore, the separated soul can understand separate substances, its happiness would be secured by its separation alone ”

“ Knowledge, therefore, acquired in the present life does not remain in the separated soul, as regards what belongs to the sensitive powers; but as regards what belongs to the intellect itself, it must remain ”

“ That the dead appear to the living in any way whatever is either by the special dispensation of God; in order that the souls of the dead may interfere in affairs of the living---and this is to be accounted as miraculous. Or else such apparitions occur through the instrumentality of bad or good angels, without the knowledge of the departed; as may likewise happen when the living appear, without their own knowledge, to others living, as Augustine says in the same book. ”

“ Hence it is that God by His one Essence understands all things; while the superior intellectual substances understand by means of a number of species, which nevertheless are fewer and more universal and bestow a deeper comprehension of things, because of the efficaciousness of the intellectual power of such natures: whereas the inferior intellectual natures possess a greater number of species, which are less universal, and bestow a lower degree of comprehension, in proportion as they recede from the intellectual power of the higher natures. ”

“ Hence the angels, by reason of their perfect intellect, through these species, know not only the specific natures of things, but also the singulars contained in those species; whereas separated souls by these species know only those singulars to which they are determined by former knowledge in this life, or by some affection, or by natural aptitude, or by the disposition of the Divine order; because whatever is received into anything is conditioned according to the mode of the recipient.
Reply to Objection 1: The intellect does not know the singular by way of abstraction ”

“ This will appear if we consider that every intellectual substance possesses intellective power by the influence of the Divine light, which is one and simple in its first principle, and the farther off intellectual creatures are from the first principle so much the more is the light divided and diversified, as is the case with lines radiating from the centre of a circle. ”

“ Gregory and Augustine, however, seem to be divided in opinion as regards the souls of the blessed in heaven, for Gregory continues the passage above quoted: "The case of the holy souls is different, for since they see the light of Almighty God, we cannot believe that external things are unknown to them." ”

“ Further, the dead often appear to the living, asleep or awake, and tell them of what takes place there; as Samuel appeared to Saul (1 Kings 28:11) . But this could not be unless they knew what takes place here. Therefore they know what takes place on earth.
Objection 3: Further, separated souls know what happens among themselves. If, therefore, they do not know what takes place among us, it must be by reason of local distance ”