The Holy Spirit is not an ignorant but a wise Being; not an agent that is moved by unenlightened impulse, but by perfect knowledge. And this being the case, it is a natural supposition and one which will be generally assented to, that his operations will always exist in accordance with, and not in opposition to the laws of the human mind.
And furthermore, according to the Scriptures, a primary and leading office, though not the only office, of the Holy Spirit is to TEACH men, to lead them into the TRUTH. And if so, then, ordinarily, the first operation will be upon the intellect, in distinction from the sensibilities and the will. And we do not hesitate to say in point of fact, and as a matter of personal experience, that the person who is guided by the Holy Spirit, will find that this divine Agent does, in reality, impart an increased clearness to the intellectual or cognitive part of the mind. This divine operation is, for the most part, very gentle and deeply interior; revealing itself by its results more than by the mere mode of its action; but it is not, on that account, any the less real. It seems to put a keenness of edge, if, we may so express it, upon the natural perceptivity, so as to enable it to separate idea from idea, proposition from proposition; and thus to guide it, with a remarkable niceness of discrimination, through the perplexities of error into the regions of truth.
We repeat, therefore, that one evidence, of being guided by the Holy Spirit, is, that such guidance contributes to the highest rationality. In other words, the person, who is guided by the Holy Spirit, other things being equal, will be the most keenly perceptive, judicious, and rational. Not flighty and precipitate; not prejudiced, one-sided, and dogmatical, but like his great inward teacher, calmly and divinely cognitive. The experience of holy men, particularly of those who have made it a practice to ask the guidance of the Holy Spirit on their studies, agrees with this statement.
— edited from The Interior or Hidden Life (2nd edition, 1844) Part 3, Chapter 6.