 Alcmaeon has been somewhat neglected in recent scholarship on early Greek philosophy (e.g., he hardly appears in Curd and Graham 2008, Long 1999 and Taylor 1997, the most recent surveys of the subject, but both Guthrie 1962 and now Zhmud 2012a and 2014 stress his importance). There would appear to be several reasons for this neglect. First, what remains of Alcmaeon’s book has little to say on the metaphysical questions about the first principles of the cosmos and about being, which have dominated recent scholarship on the Presocratics. Second, doubts about his date and about the focus of his investigations have made it difficult to place him in the development of early Greek thought. Finally, a more accurate appreciation of his use of dissection has deflated some of the hyperbolic claims in earlier scholarship about his originality. The extent of his originality and the importance of his influence depend to a degree on his dating. An extremely late dating for his activity (after 450 BCE) makes him appear to espouse the typical views of the age rather than to break new ground. If he was active in the early fifth century, his views are much more original. That Aristotle wrote a separate treatise in response to Alcmaeon argues in favor of his originality. He should probably be regarded as a pioneer in applying a political metaphor to the balance of opposites that constitute the healthy human body. The range of his work in biology is remarkable for the early fifth century and he may have initiated a physiological emphasis in Greek philosophy which was not present in Ionian philosophers, such as Anaximander and Anaximenes, and set the agenda in this area for later Presocratics (Zhmud 2012a, 366). It is sometimes said that his conception of poroi (channels), which connect the sense organs to the brain, influenced Empedocles’ theory of poroi, but the theories may share no more than the name. In Empedocles, all materials have pores in them, which determine whether they mix well with other objects. Sense organs also have pores, but these function not to connect the sense organ to the seat of intelligence (which for Empedocles is the heart) but to determine whether the sense organ can receive the effluences that are poured forth by external objects (Solmsen 1961, 157; Wright 1981, 230). Alcmaeon’s influence was significant in three final ways: 1) His identification of the brain as the seat of human intelligence influenced Philolaus (DK, B13), the Hippocratic Treatise, On the Sacred Disease, and Plato (Timaeus 44d), although a number of thinkers including Empedocles and Aristotle continued to regard the heart as the seat of perception and intelligence. 2) His empiricist epistemology may lie behind important passages in Plato (Phaedo 96b) and Aristotle (Posterior Analytics 100a). 3) He developed the first argument for the immortality of the soul, which may have influenced Plato’s argument in the Phaedrus (245c ff.).