For cult purposes, then—the primary purpose of Greek religion—there was less difference between gods than we might suppose. Not even the strongly marked personages that poetry made of them were able to fix themselves in the popular mind. Sculptors had been busy in differentiating types, and yet even here the process was not completed. While in general we know of Poseidon-types, Zeus-types, etc., in art, the most thoroughly equipped critics find themselves embarrassed if they are required to name a statue that is wholly lacking in definite external symbols or attributes, such as the thunderbolt, trident, caduceus, and others.[10] Even the unrivaled artistic abilities of Greek sculptors found it impossible to create unmistakable types of the Greek gods, for the reason that the character of the god as portrayed in myth and fable was fluid, and not fixed. As among most peoples of the time, the essential religious act was that which brought the god and his worshiper into contact—the sacrifice. What the real nature of sacrifice was need not concern us here. The undoubted fact is that sacrifice and prayer formed a single act;[11] that it was during the sacrifice that the worshiper ventured to address his prayer to the godhead he invoked. In doing so he must of necessity use the god’s name, and, as we have seen, the name was of more general and less specific connotation than is usually supposed. But the act of worship itself was specifically occasioned. Even the fixed and annually recurring festivals related to a specific, if recurring, occasion in the life of the people. This was eminently the case in the irregular acts of worship that arose out of some unforeseen contingency. Whatever the divine name was that was used, the specific occasion of its use made it necessary also to specify the function of the divinity of which the intervention was sought. That was regularly done by attaching to the name a qualifying epithet. When the rights of hospitality were threatened with invasion, it was Ζεὺς Ξένιος, Zeus the Protector of Strangers, that was addressed. In gratitude for a deliverance, Zeus or Apollo or Heracles or the Dioscuri or many another might be invoked as “the Savior.”[12] And it might well be argued that the Greek who did so had scarcely anything more definite in mind than a Roman who worshiped Salus, the abstract principle of safety. In very many cases the particular function was especially potent in certain areas, so that a local adjective applied as a divine epithet would sum up the power desired to be set in motion.