''Truth is from heaven,'' declares Jesus in one of the apocryphal gospels in answer to Pilate's derisive question, an answer omitted from the four canonical Gospels. Truth is indeed from heaven, from the overworld of diviner ideality. It is inscribed upon the imperishable tablets of cosmic mind. What the individual mind grasps of its eternal principles is never lost. But at each dip of the soul into incarnation it loses its paradise of knowledge and understanding as it plunges deep into the heart of matter and is buried in the underworld of sense. Paradise must be regained each time with the return of the consciousness to the levels of former development, and new glories won. And so we have the great Plato giving us the twin doctrines of ''the loss of memory of divine things'' and ''reminiscence,'' or recovery of divine memory.