In his book Endowments of Man, Archbishop Ullathorne explains that God gives us just the right amount of knowledge to allow us to choose whether or not to believe:
“All things in the creation have their lights and shadows. There is nothing in this visible world, from the sun in the heavens to the pebble that rolls under our feet; from the man with whom we are familiar to the insect we examine with the microscope, that has not one side in light and another that is in obscurity.”
“Whatever we know in this world, whether by perception or by the testimony of others, is partly known and partly unknown; yet we have sufficient knowledge to secure certainty, sufficient for conviction, for assent, for belief, and for our guidance. And nothing can be more irrational, nothing more unphilosophical, than to argue from the obscure against the clear side of any fact or truth, as if the one was the denial of the other; whereas that which is clear vouches for that which is obscure in one and the same subject. Yet this is the common method of sceptics and unbelievers.”
“But if our natural knowledge presents us with both lights and shadows; with clear evidence, attended by obscurities beyond the reach of our limited mind and faculties; how much more must we expect this to be the case when our minds are brought into contact with the divine and supernatural truths of revelation.”
“Nor must it be forgotten, that in this divine economy of revelation, the God of heaven contemplates a two fold purpose: the one to enlighten us with divine truth, and to guide us by that light on our way to heaven; the other to try our faith and obedience.”
“The light given with divine revelation is so tempered that the good may use it with confidence, and are never without sufficient light, whilst it is within the power of the evil-disposed to refuse that light. For God has made His revelation the text and trial of truth, whether we will freely accept His truth by faith or not. There is light enough, and much more than enough, to test spirits of those who are proud-minded and unwilling to see. There is light to enlighten the faithful and obscurity to humble them. There is obscurity enough for the unfaithful man to blind himself with, whilst there is light enough to condemn him for his willing blindness. There is brightness enough in the doctrines of faith to make our belief reasonable, and darkness enough to make our adhesion a meritorious obedience and an act of fidelity to divine authority.”
Quotations from Michael F. Glancey, Characteristics From the Writings of Archbishop Ullathorne (London: Burns & Oates, 1889).