461. It has been said that spirits hunger, thirst, and stand in need of repose. It is true that those states do pertain to spirit life agreeably to the law of spiritual correspondences. The grosser and more undeveloped the spirit, the closer is the analogy between it and the physical states. 462. Physical laws and substances are gross or externalized spiritual laws and things. The more refined and developed the spirit, the less it requires of gross aliment. Refined, intellectual, and moral beings are nourished and sustained by refined, intellectual, and moral nutriment. Their food is derived from the “Tree of Knowledge,” and they slake their thirst at the crystal streams which continually flow from the inexhaustible fountain of God’s wisdom and love. The lowest undeveloped spirit lives on comparatively refined aliment to that on which mortals subsist. It consists of the more refined elements of spiritual fruits and vegetables. The spirit’s need of rest depends on its particular degree of development, diminishing in proportion to its advancement from the material plane. 463. Though the principles embodied in our teachings and philosophy may be regarded, by the majority of mankind, as _strange_ and incomprehensible, they are, nevertheless, no more so than the principles of natural science would be to the unlettered mind. As the ability to comprehend the principles on which the natural sciences are based increases with the expansion of the intellectual faculties, in like manner is the power of perceiving spiritual things and relations increased by the development of the interior or spiritual faculties. 464. As there are no words in the human language in which spiritual ideas may be embodied so as to convey their literal and exact signification, we are obliged ofttimes to have recourse to the use of analogisms and metaphorical modes of expression. In our communion with you we have to comply with the peculiar structure and rules of your language; but the genius of our language is such that we can impart more ideas to each other in a single word than you can possibly convey in a hundred. 465. I have thus given you a general outline of the leading facts connected with the destiny of the race. I have endeavoured to show you that man is a progressive being, that he possesses a refined material (449) organization, which, going with him at death, serves as a medium through which he may communicate with the visible world. I will here add that, under certain circumstances, this spiritual organization has the power of reflecting the rays of light, so as to be rendered visible to the natural eye, as are certain gaseous bodies.