33 Finally, they reproach this philosophy taught in our schools for regarding only the intellect in the process of cognition, while neglecting the function of the will and the emotions. This is simply not true. Never has Christian philosophy denied the usefulness and efficacy of good dispositions of soul for perceiving and embracing moral and religious truths. In fact, it has always taught that the lack of these dispositions of good will can be the reason why the intellect, influenced by the passions and evil inclinations, can be so obscured that it cannot see clearly. Indeed St. Thomas holds that the intellect can in some way perceive higher goods of the moral order, whether natural or supernatural, inasmuch as it experiences a certain "connaturality" with these goods, whether this "connaturality" be purely natural, or the result of grace; and it is clear how much even this somewhat obscure perception can help the reason in its investigations. However it is one thing to admit the power of the dispositions of the will in helping reason to gain a more certain and firm knowledge of moral truths; it is quite another thing to say, as these innovators do, indiscriminately mingling cognition and act of will, that the appetitive and affective faculties have a certain power of understanding, and that man, since he cannot by using his reason decide with certainty what is true and is to be accepted, turns to his will, by which he freely chooses among opposite opinions.
Source: Humani Generis (Vatican.va)