But it will be said that the objection which has been brought against us has not yet been solved, and that what unbelievers have urged has been rather strengthened by all we have said. For if, as our argument has shown, there is such power in Him that both the destruction of death and the introduction of life resides in Him, why does He not effect His purpose by the mere exercise of His will, instead of working out our salvation in such a roundabout way, by being born and nurtured as a man, and even, while he was saving man, tasting death; when it was possible for Him to have saved man without subjecting Himself to such conditions?
Now to this, with all candid persons, it were sufficient to reply, that the sick do not dictate to their physicians the measures for their recovery, nor cavil with those who do them good as to the method of their healing; why, for instance, the medical man felt the diseased part and devised this or that particular remedy for the removal of the complaint, when they expected another; but the patient looks to the end and aim of the good work, and receives the benefit with gratitude.
Seeing, however, as says the Prophet, that God's abounding goodness keeps its utility concealed, and is not seen in complete clearness in this present life— otherwise, if the eyes could behold all that is hoped for, every objection of unbelievers would be removed—but, as it is, abides the ages that are coming, when what is at present seen only by the eye of faith must be revealed, it is needful accordingly that, as far as we may, we should by the aid of arguments, the best within our reach, attempt to discover for these difficulties also a solution in harmony with what has gone before.
Source: The Great Catechism (New Advent)