Objection 1: It seems that it is not manful to weep. For to be manful is to possess qualities befitting a man. And of the qualities most befitting a man (vir) are the virtues (virtutes). But the virtues are good habits which participates in reason, as the Angelic Doctor shows (Summa Theologiae, I-II. q. 55, a. 4c). But when one is in the midst of strong weeping the use of reason is hindered, and thus too are the virtues hindered. Thus weeping is not manful.
Objection 2: As was stated above, that which is manful is that which is virtuous for a man. But in his Confessions (IX.xii), St. Augustine tells how he fought back tears at the death of his mother St. Monica. Now, Saints are those who possess "heroic virtue." Thus it is not manful to weep.
Sed contra: The Evangelist John states: "And Jesus wept" (John xi.35). But our Lord is without vice or sin. Thus it cannot necessarily be contrary to virtue and right reason to weep, and thus it cannot be unmanful.
Respondeo dicendum: As has been stated, that which is manful is that which befits a man, and that which most befits a man is virtue. Thus the question is whether weeping is contrary to virtue. And to this we must answer as follows: to weep follows from sorrow or pain. Now, sorrow or pain are passions and passions are specified by their objects. Thus it would follow that whether or not particular pain or sorrow is virtuous is dependent upon whether or not the object over which one feels pain or sorrow is one for which it would be proper to feel pain or sorrow according to right reason. Now, insofar as one feels pain and sorrow properly and in accord with right reason, it would not be vicious to weep on account of said pain or sorrow. And thus it would not be unmanful to weep insofar as one feels pain or sorrow in accord with right reason. For example, it would not be unmanful to weep on account of one's sins.
Reply to Objection 1: The Angelic Doctor states that "it is not contrary to virtue, if the act of reason be sometimes interrupted for something that is done in accordance with reason, else it would be against virtue for a person to set himself to sleep" (Summa Theologiae, I-II. q. 153, a. 2 ad 2). Thus, insofar as the pain or sorrow one feels is in accord with right reason, and insofar as one weeps in accord with right reason, i.e. one does not allow weeping to hinder one from performing acts of virtue and duty that one is required to perform, then weeping is not contrary to right reason even if it interrupts reason.
Reply to Objection 2: St. Augustine, in the same place, informs us that he did not weep openly and in public because "in most cases it is customary to use such mourning to imply sorrow for the miserable state of those who die, or even their complete extinction. But my mother's dying meant neither that her state was miserable nor that she was suffering extinction" (Confessions IX.xii). However he later wept for his mother while bathing in private. Thus the Saint refrained from weeping for the death of his mother not because it was vicious per se, but because to do so publicly would have caused scandal by leading others to believe that St. Monica was rendered miserable or extinct by her death.