In Nordhoff's Communistic Societies of the United States, he quotes a definition of "Perfectionism" he received from the Oneida Community:
"As the doctrine of temperance is total abstinence from alcoholic drinks, and the doctrine of anti-slavery is immediate abolition of human bondage, so the doctrine of Perfectionism is immediate and total cessation from sin.
"But the analogy thus suggested between Perfectionism and two popular reforms is by no means to be regarded as defining the character of Perfectionism. Salvation from sin, as we understand it, is not a system of duty-doing under a code of dry laws, Scriptural or natural; but it is a special phase of religious experience, having for its basis spiritual intercourse with God.
"...[F]aith leads [us] to seek intercourse with [God], to approach him by prayer, to give him [our] hearts, to live in communion with him. These exercises and the various states and changes of the inner life connected with them constitute the staple of what is commonly called religious experience... Perfectionists hold that intercourse with God may proceed so far as to destroy selfishness in the heart, and so make an end of sin. This is the special phase of religious experience which we profess..." (Nordhoff, The Perfectionists of Oneida)
Not a system, not obedience to a code, but a phase of experience. Not a model but a set of exercises and the various states and changes of the inner life connected with them. The key is practice. This seems to me quite similar to Arizmendiarrieta's emphasis on cooperativism as an experience. Arizmendiarrieta, too, was influenced by a doctrine of "perfectionism" in which the task of the priest was to destroy selfishness in the heart.
The interesting question to me is what to make of all this from a non-religious standpoint? I think the basic epistemological problem is the same: grounding a project not in models but in experience, making it at once radically contingent and transcendent, an experience which is at heart a constant practice of liberation.