The part which creative imagination and intuition play in framing scientific hypotheses when disciplined by a logical habit of mind, is strikingly illustrated in the views of some of the early Greek philosophers. For though they did not understand the method of empirical science, and had no mechanical aids, they adumbrated the two most fruitful hypotheses of modern science, evolution and the atomic structure of matter. In the latter case they did more than adumbrate the conception, they worked it out in detail. In the work of the Roman poet Lucretius the atomic view of nature was finally presented as a complete interpretation of the universe.