God is not more the center of the life of the soul, than he is the center of all truth; that is to say, he does not move the soul more to right action, than he does to right perception. When God is displaced from his center in the soul, the relations of truth, considered as the subjects of our perceptions, are entirely unsettled. It is then that man, cast as it were on an ocean without soundings and without shore, knows not where he is, nor what he is. He resorts to reasoning, therefore, from the necessity of his position. So great are his perplexities, that he is obliged to reason. He doubts, he inquires, he compares, he draws conclusions, he pronounces judgment. His whole mental nature is in action, without its being the action of rest, the quiet movement of the divine order. Perhaps it is well that it should be so, until, by making inquiries without results, and without finding the true rest of the spirit, he feels the necessity of turning to God in humility, who is the only source of truth for the understanding, and of pacification for the heart.
It is different with the truly holy soul. The soul, which is united with God in the full exercise of faith, rests from reasonings.
In order to understand this proposition, however, it is proper to say something in explanation of the terms used in it. The term REST is relative. It has relation to and implies the existence of the opposite, namely, unquietness or unrest. The term REASONING, is the name of that important intellectual power which compares and combines truth, in order to discover new truth. Under a divine direction, this power is susceptible of useful applications and results. It is then entirely calm in its action, and is consistent with the highest peace and joy of the spirit. To rest from such reasonings, from reasonings which do not disturb rest, would be an absurdity. Such rest would be cessation from action, and not rest or quietude in action. When, therefore, the remark is made by spiritual writers, that the truly renewed soul has rest from reasonings, the meaning is, that it has rest from the vicious and perplexing reasonings of nature; in other words, from reasonings which are not from God. It is certainly a great religious grace to be free from such reasonings.
He who has no rest, except what he can find in reasonings, (we mean such reasonings as have just been described,) can never enjoy the true rest, because such reasoning never can give it. It is not an instrument adequate to such a result. And it may properly be added here, that there are some mysteries in the universe which reasoning, in any of its forms, has not power to solve. To a created mind, for instance, a mind which is uncreated must always be a mystery. From the nature of the case, God is a mystery to the human mind, because, being uncreated, he is, and always must be, incomprehensible. Incomprehensible in his nature, he is incomprehensible also in many of his creative and administrative acts. The apostle, in speaking of the depths of God's wisdom, exclaims: "How unsearchable are his judgments, and his ways past finding out!" Rom. 11: 33. Well may those judgments be called unsearchable, and those ways past finding out, which pertain to the Infinite, It is obviously impossible that the finite should fully explore them.
— edited from A Treatise on Divine Union (1851) Part 8, Chapter 2.