If knowledge is gained by means of sensation, then which senses combine to cause my perception of an eye? And, what is more, how can one validly infer from that perception the proposition “The perception of an eye is caused by the combined sensations x,y, and z”? And again, if all that is perceived undergoes change, then which perception is to serve as the template for all subsequent experiences of what is perceived? How can one validly infer that template A is correct and template B is not? As a Christian, I do not deny that we have ideas of such things; however, I deny that our sensation plays any role in the acquisition of knowledge. For all induction is fallacious; therefore, no general conclusion can be validly inferred via inductive reasoning.
Moreover, it is useless to argue, as some do, that this criticism only applies to inductive reasoning as it applies to the movement from particulars to universals; for if A is A, then it perpetually remains itself. And if it perpetually remains itself, then it perpetually exhibits at least one quality by which it may be identified as A, in contradistinction to ~A, B, b, etc. And if it must exhibit at least one quality that perpetually obtains in itself, then it must remain so at all times and under all conditions. Consequently, particulars are universals in the sense that they must remain themselves at all times, at all places, and under all conditions. Thus, the problem of induction ever penetrates that last refuge of the empiricists. It is only wishful thinking that would have us believe otherwise.
It is only wishful thinking, I say, to believe that sensibles are responsible for our ideas, for if A is universally A, but my sensations differ from moment to moment, and my perception likewise differs from moment to moment, then upon what logical basis do I infer that (I.)there is actually an A for me to know and that (ii.) A remains itself from moment to moment and day to day? How do I know that A is A? Contrary to the thinking of many, it cannot be by means of appealing to sensibles, for I can only call a sensible “A” by means of presupposing that (I.)it is and (ii.)it remains itself from moment to moment and day to day. Therefore, even the conception of “A,” which implies the law of contradiction and further the law of excluded middle, is not derived from sensibles. Rather, what is sensible is known by means of the intellect. To state this matter in an even clearer manner: If sensibles are necessary to the acquisition of knowledge, then how do angels know the affairs of men, seeing as they are spirits and spirits do not have flesh and bone (i.e. they do not have physical sensations of sensibles)?
But perhaps more damningly: If sensibles are necessary to the acquisition of knowledge, then how did Adam and Eve understand these words addressed to them on the day of their creation:
“Be fruitful and multiply and fill the earth and subdue it, and have dominion over the fish of the sea and over the birds of the heavens and over every living thing that moves on the earth”?[ Gen 1:28]
For the commands here concern things which they have never before done nor seen nor heard had been done by anyone else (for there was no one else but God!). From what experience of sensibles did Adam and Eve acquire a knowledge of sexual intercourse? Of fruitfulness? Of multiplication? Of dominion? They had experienced none of these things. Just as they had never experienced eating, and yet the Lord declares to the couple:
“Behold, I have given you every plant yielding seed that is on the face of all the earth, and every tree with seed in its fruit. You shall have them for food. And to every beast of the earth and to every bird of the heavens and to everything that creeps on the earth, everything that has the breath of life, I have given every green plant for food.”
Or to press this matter even further, I ask: If sensibles are necessary to the acquisition of knowledge, how did Adam and Eve have a knowledge of human language? At the moment of their coming into existence, God speaks to them and they understand His speech. How is this possible if sensibles are necessary to the acquisition of knowledge?
If sensibles are necessary to the acquisition of knowledge, then would it not be impossible for God to have spoken to man and woman in the manner quoted above, but also to have placed man in the garden of Eden “…to work it and keep it…”[ Gen 2:15b]? How could Adam be placed in the garden to work with that which he had never before experienced? How could he keep that which he had no knowledge of? What is worse, I ask: If sensibles are necessary to the acquisition of knowledge, then upon what basis did God hold man responsible for upholding the law or transgressing it? Adam knew that he had been created to be in covenant relationship to God – how then could he have known this as there were no other covenants which he could observe and obtain a general concept of?
It goes without saying that it is not only logically impossible for knowledge to be dependent upon sensibles in any way, it is also Scripturally shown to be false. For Adam and Eve had no experiences, but they understood some very complex ideas! How then did man know? How does man know? In a word, it is by revelation: God speaks and man understands, for man is made in the image of God, a rational being who was made to be in covenant with God. Man, therefore, knows what God has revealed. Sensibles are real, but they do not impart, suggest, or impart to us knowledge of the world. Rather, the Scripture says: “Do not boast about tomorrow, for you do not know what a day may bring.”[ Prov 27:1] And again: “In the morning sow your seed, and at evening withhold not your hand, for you do not know which will prosper, this or that, or whether both alike will be good.”[ Ecc 11:6] Additionally, the Lord says: “…you do not know what tomorrow will bring…”[ James 4:14a]
Now if the Scriptures support the idea that sensibles are necessary for knowledge, then the problem is made greater by the Scriptures just quoted. For each of them denies that one can have knowledge of the future.