Our investigation of the facts of our religion will give us a reasoned and scientific knowledge of those things which the Prophets taught us dogmatically, and will enable us to answer the arguments and criticisms of our opponents directed against our faith. Hence it is not merely our privilege but our duty to confirm the truths of religion by reason.[49] Here a question presents itself. If the reason can discover by itself the truths communicated to us by divine revelation, why was it necessary to have recourse to the latter? Why was it not left to the reason alone to guide us in our belief and in our conduct? The answer is, as was suggested before, that human reason proceeds gradually and does not reach its aim until the end of the process. In the meantime one is left without a guide. Besides not everybody's reason is adequate to discover truth. Some are altogether incapable of this difficult task, and many more are exposed to harassing doubts and perplexities which hinder their progress. Hence the necessity of revelation, because in the witness of the senses all are equally at home, men and women, young and old.[50] The most important fact of religion is the existence of God. We know it from the Bible, and we must now prove it by reason. The proof is necessarily indirect because no one of us has seen God, nor have we an immediate certainty of his existence. We must prove it then by the method of inference. We must start with something we do know with certainty and proceed from it through as many steps of logical inference as may be necessary until we reach the object of our search.[51]