I answer that, The pleasure of contemplation can be understood in two ways.  In one way, so that contemplation is the cause, but not the object of pleasure:  and then pleasure is taken not in contemplating but in the thing contemplated.  Now it is possible to contemplate something harmful and sorrowful, just as to contemplate something suitable and pleasant.  Consequently if the pleasure of contemplation be taken in this way, nothing hinders some sorrow being contrary to the pleasure of contemplation.

In another way, the pleasure of contemplation is understood, so that contemplation is its object and cause; as when one takes pleasure in the very act of contemplating.  And thus, according to Gregory of Nyssa [Nemesius, De Nat.  Hom. xviii.], “no sorrow is contrary to that pleasure which is about contemplation”:  and the Philosopher says the same (Topic. i, 13; Ethic. x, 3).  This, however, is to be understood as being the case properly speaking.  The reason is because sorrow is of itself contrary to pleasure in a contrary object:  thus pleasure in heat is contrary to sorrow caused by cold.  But there is no contrary to the object of contemplation:  because contraries, as apprehended by the mind, are not contrary, but one is the means of knowing the other.  Wherefore, properly speaking, there cannot be a sorrow contrary to the pleasure of contemplation.  Nor has it any sorrow annexed to it, as bodily pleasures have, which are like remedies against certain annoyances; thus a man takes pleasure in drinking through being troubled with thirst, but when the thirst is quite driven out, the pleasure of drinking ceases also.  Because the pleasure of contemplation is not caused by one’s being quit of an annoyance, but by the fact that contemplation is pleasant in itself:  for pleasure is not a “becoming” but a perfect operation, as stated above (Q. 31, A. 1).

Accidentally, however, sorrow is mingled with the pleasure of contemplation; and this in two ways:  first, on the part of an organ, secondly, through some impediment in the apprehension.  On the part of an organ, sorrow or pain is mingled with apprehension, directly, as regards the apprehensive powers of the sensitive part, which have a bodily organ; either from the sensible object disagreeing with the normal condition of the organ, as the taste of something bitter, and the smell of something foul; or from the sensible object, though agreeable, being so continuous in its action on the sense, that it exceeds the normal condition of the organ, as stated above (Q. 33, A. 2), the result being that an apprehension which at first was pleasant becomes tedious.  But these two things cannot occur directly in the contemplation of the mind; because the mind has no corporeal organ:  wherefore it was said in the authority quoted above that intellectual contemplation has neither “bitterness,” nor “tediousness.”  Since, however, the human mind, in contemplation, makes use of the sensitive powers of apprehension, to whose acts weariness is incidental; therefore some affliction or pain is indirectly mingled with contemplation.