Ante-Nicene Fathers, Vol VII:
Lactantius: Chap. III.—Of what subjects philosophy consists, and who was the chief founder of the academic sect

Chap. III.—Of What Subjects Philosophy Consists, and Who Was the Chief Founder of the Academic Sect.

Philosophy appears to consist of two subjects, knowledge and conjecture, and of nothing more. Knowledge cannot come from the understanding, nor be apprehended by thought; because p. 71 to have knowledge in oneself as a peculiar property does not belong to man, but to God. But the nature of mortals does not receive knowledge, except that which comes from without. For on this account the divine intelligence has opened the eyes and ears and other senses in the body, that by these entrances knowledge might flow through to the mind. For to investigate or wish to know the causes of natural things,—whether the sun is as great as it appears to be, or is many times greater than the whole of this earth; also whether the moon be spherical or concave; and whether the stars are fixed to the heaven, or are borne with free course through the air; of what magnitude the heaven itself is, of what material it is composed; whether it is at rest and immoveable, or is turned round with incredible swiftness; how great is the thickness of the earth, or on what foundations it is poised and suspended,—to wish to comprehend these things, I say, by disputation and conjectures, is as though we should wish to discuss what we may suppose to be the character of a city in some very remote country, which we have never seen, and of which we have heard nothing more than the name. If we should claim to ourselves knowledge in a matter of this kind, which cannot be known, should we not appear to be mad, in venturing to affirm that in which we may be refuted? How much more are they to be judged mad and senseless, who imagine that they know natural things, which cannot be known by man! Rightly therefore did Socrates, and the Academics 374 who followed him, take away knowledge, which is not the part of a disputant, but of a diviner. It remains that there is in philosophy conjecture only; for that from which knowledge is absent, is entirely occupied by conjecture. For every one conjectures that of which he is ignorant. But they who discuss natural subjects, conjecture that they are as they discuss them. Therefore they do not know the truth, because knowledge is concerned with that which is certain, conjecture with the uncertain.  

Let us return to the example before mentioned. Come, let us conjecture about the state and character of that city which is unknown to us in all respects except in name. It is probable that it is situated on a plain, with walls of stone, lofty buildings, many streets, magnificent and highly adorned temples. Let us describe, if you please, the customs and deportment of the citizens. But when we shall have described these, another will make opposite statements; and when he also shall have concluded, a third will arise, and others after him; and they will make very different conjectures to those of ours. Which therefore of all is more true? Perhaps none of them. But all things have been mentioned which the nature of the circumstances admits, so that some one of them must necessarily be true. But it will not be known who has spoken the truth. It may possibly be that all have in some degree erred in their description, and that all have in some degree attained to the truth. Therefore we are foolish if we seek this by disputation; for some one may present himself who may deride our conjectures, and esteem us as mad, since we wish to conjecture the character of that which we do not know. But it is unnecessary to go in quest of remote cases, from which perhaps no one may come to refute us. Come, let us conjecture what is now going on in the forum, what in the senate-house. That also is too distant. Let us say what is taking place with the interposition of a single wall; 375 no one can know this but he who has heard or seen it. No one therefore ventures to say this, because he will immediately be refuted not by words, but by the presence of the fact itself. But this is the very thing which philosophers do, who discuss what is taking place in heaven, but think that they do that with impunity, because there is no one to refute their errors. But if they were to think that some one was about to descend who would prove them to be mad and false, they would never discuss those subjects at all which they cannot possibly know. Nor, however, is their shamelessness and audacity to be regarded as more successful because they are not refuted; for God refutes them to whom alone the truth is known, although He may seem to connive at their conduct, and He reckons such wisdom of men as the greatest folly.  

Footnotes

It is evident that the Academy took its rise from the doctrine of Socrates. Plato, the disciple of Socrates, founded the Academy. However excellent their system may appear to many, the opinion of Carneades the Stoic seems just, who said that “the wise man who is about to conjecture is about to err, for he who conjectures knows nothing.” Thus knowledge is taken from them by themselves.—Betul.  

With nothing but an inner wall between.