This is not a book of theology, and I have no intention of dilating on these things. It must, however, be manifest to all who are acquainted with contemporary thought how largely these influences have displaced theological beliefs among great numbers of educated men; how many things that were once widely believed have become absolutely incredible; how many that were once supposed to rest on the plane of certainty have now sunk to the lower plane of mere probability or perhaps possibility. From the time of Galileo downwards, these changes have been denounced as incompatible with the whole structure of Christian belief. No less an apologist than Bishop Berkeley declared that the belief that the date of the existence of the world was approximately that which could be deduced from the book of Genesis was one of the fundamental beliefs which could not be given up.[58] When the traveller Brydone published his travels in Sicily in 1773, conjecturing, from the deposits of lava, that the world must be much older than the Mosaic cosmogony admitted, his work was denounced as subverting the foundations of the Christian faith. The same charges were brought against the earlier geologists, and in our own day against the early supporters of the Darwinian theory; and many now living can remember the outbursts of indignation against those who first introduced the principles of German criticism into English thought, and who impugned the historical character and the assumed authorship of the Pentateuch. It is not surprising or unreasonable that it should have been so, for it is impossible to deny that these changes have profoundly altered large portions of the beliefs that were once regarded as essential. One main object of a religion was believed to have been to furnish what may be called a theory of the universe--to explain its origin, its destiny, and the strange contradictions and imperfections it presents. The Jewish theory was a very clear and definite one, but it is certainly not that of modern science.