Q. What is an apikoros?A. It means “unbeliever”. Using this epithet is an insult only if you intend it to be such. But though an apikoros is missing out on the inspiration that comes from being a believer, no-one can be forced to believe, and you cannot argue them into belief.
Homiletically, the word derives from pakar, “to break forth”, and hence it is someone who rebels against traditional religion; an associated word, hefker, means free or abandoned. Historically, the name is from the Greek philosopher Epicurus (341-270 BCE), who believed that with the correct philosophy of life a person could reach “quietude of mind and steadfast faith”. Associated with his name is the view that though the universe is eternal and infinite, nothing is created out of nothing and nothing passes into nothing. The soul is destructible; pleasure is the beginning and end of the good life. The existence of God or the gods is not denied, but God (or the gods) do not control the world or feel concern for man. (See Josephus, Antiquities 10:11:7; cf. Maimonides, Guide for the Perplexed 3:17).
Judaism found this problematical. It preferred seriousness and moral strictness to pleasure and indulgence. It believed not only that God was the Creator but that His Providence continued to rule the creation. It could not accept that God had abandoned His world and left it hefker, ownerless. It developed a firm doctrine of the two worlds – this world and the World to Come. It applied the term apikoros to anyone who rejected these basic Jewish doctrines and warned that the apikoros had no share in the World to Come (Mishnah Sanh. 10:1).
In due course it extended the meaning of the term very widely to anyone who did not show respect to the sages. Me’iri (13th cent.)
defines an apikoros as one who despises a learned person and his learning and thus denies the things he should believe in (commentary to Sanh. 90a).
To Maimonides (Hilchot T’shuvah, chapter 3), an apikoros rejects prophecy and the prophetic status of Moses, and denies that God knows the deeds of human beings. The Shulchan Aruch adds that the apikoros not only lacks belief but transgresses the law on purpose, e.g. by eating forbidden food or wearing sha’atnez, a prohibited mixture of textiles (CH.M. 425:5).
There is a distinction between an apikoros and an am ha’aretz, an ignoramus. An unbeliever who is also an ignoramus is a major problem, because he does not know what it is that he does not believe in. Hence when the Mishnah says that one must know what to answer an apikoros (Avot 2:14), it may be saying that he must not be allowed to remain uninformed.