SPEAKING to the Durham University Philosophical Society on February 1 at Armstrong College, New-castle-upon-Tyne, Dr. Herbert Dingle, assistant professor of astrophysics at the Imperial College of Science and Technology, gave a historical account of the development of our ideas of the structure of the universe. Defining the ‘universe’ as the whole of physical existence, he pointed out that this apparently general subject demands a treatment which is in many respects unique. The idea of infinity became general with the Renaissance, and this seemed to place the conception of the whole universe beyond the power of the finite mind, until Newton restored the possibility with his implicit concept of universal law which was everywhere applicable. There have been two criticisms of this; a valid objection, that this extension of locally derived law may be incorrect; and an invalid one, based on our imperfect knowledge of atomic processes, which ignores the fact that the laws of a whole can be arrived at without combining the laws of elementary parts. Towards the end of last century, it was argued that the Newtonian law of gravitation was inconsistent with an infinite extension of uniformly distributed matter, of however low a density. Relativity theory, however, made such homogeneity acceptable. The Einstein, de Sitter and expanding universes are widely known nowadays, but Dr. Dingle made it clear that there is nothing esoteric about such theories, and that their underlying principles might have been expected from recent observations even if they had not been discovered when they were. It was stated also that there is no objection to belief in an infinite space, if one is willing to admit that in Einstein's space-time it may be quite beyond physical exploration.