It is generally assumed that the Hippocratic Oath is different in spirit from most writings of the Corpus Hippocraticum (5th to 4th cent. B.C.), and therefore Edelstein has suggested that the covenant and the ethical code it contains originated in a rather exclusive group, which was strongly influenced by Pythagorean doctrine. His contention, based on quotations from various authors (including Plato and Aristotle), that its most fundamental concepts (esp. rejection of euthanasia and of abortion) were not generally accepted, is not borne out by the evidente of the medical writings of the Hippocratic era. On the contrary, it appears that, to the Hippocratics at least, these concepts were as essential for medical ethics as they are now.