Clement boldly asserts the unity of all knowledge. Everything contributes, everything is concentric. "Just as every family goes back to God the Creator, so does the teaching of all good things go back to the Lord, the teaching that makes men just, that takes them by the hand and brings them that way."[50] And again:--"When many men launch a ship, pulling together, you could not say there are many causes, but one consisting of many--for each of them is not by himself the cause of its being launched but only in conjunction with others; so philosophy, which is a search for truth, contributes to the perception (_katalepsis_) of truth, though it is not the {277} cause of perception, except in conjunction and co-operation with other things. Yet perhaps even a joint-cause we might call a cause. Happiness is one, and the virtues more than one which are its causes. The causes of warmth may be the sun, the fire, the bath and the clothing. So, truth is one and many things co-operate in the search for it, but the discovery is by the Son.... Truth is one, but in Geometry we have geometrical truth, in Music musical; so in Philosophy--right Philosophy--we should have Greek truth. But alone the sovereign Truth is unassailable, which we are taught by the Son of God."[51] Elsewhere, when challenged to say what use there is in knowing the causes that explain the sun's motion,[52] geometry and dialectics, when Greek philosophy is merely man's understanding, he falls back upon the mind's instinctive desire for such things, its free will (_ten proairesin tou nou_), and quickly marshals a series of texts from the Book of _Wisdom_ on the divine source of wisdom and God's love of it, concluding with an allegory drawn from the five barley loaves and the two fishes on which the multitude were fed, the former typifying the Hebrew Law ("for barley is sooner ripe for harvest than wheat") and the fishes Greek philosophy "born and moving amid Gentile billows." ("If you are curious, take one of the fishes as signifying ordinary education and the other the philosophy that succeeds it.... A choir of voiceless fish came sweeping on, the Tragic muse says somewhere"[53]). His appeal to the mind is a much stronger defence than any such accumulation of texts, but for the people he had in view the texts were probably more convincing.