""عقلانية الأخلاق المسيحية وتطبيقاتها التحررية عند القديس بييّر أبيلار""

Rationality of Christian Ethics and the concept of actual sin are considered among the most important ethical issues which were dealt by Pierre Abelard, the most important rationalist philosopher of ethics and theology in the Mediaeval Ages. He was distinguished by relying on reason, rebelling against the church, calling for Humanism and his reformation of the Christian thought and discourse.
Abelard has connected between ethics and theology out of his desire to liberae the Christian ethics and to raise the value of man. He made ethics rely on reason through presenting rational ethics which give a precise concept of the 'actual' sin; and in which intention, will conscience and concupiscence come first. According to him, there is no place but for the personal actual sin in which the doer take the responsibility. Thus, ignorance of some act is not considered a sin.
He applied ethics on theology that he reached many liberating results which were really an ethical and rational revolution against theology. Among the most important results are: his refusal of the Christ's Crucifiers sin, his refusal of the messengers and martyrs oppressors' sin, his refusal of the non-believers of Christianity sin, and his denial of the original sin. Therefore, he was accused of hypocrisy in Sens Commune in 1141.
The aim of this paper is to discover the thought of Pierre Abelard, the most influential liberating Christian philosopher. The paper also aims at understanding his ethical though which is very much connected with theology. One will depend on comparative analytical critical methodology in dealing with Abelard's ideas.
 The paper deals with four basic points:

Abelard concept of actual sin.
Abelard concept of intention and its effect on the actual sin.
Abelard concepts of will and concupiscence and their relation to the actual sin.
Liberating applications of Abelard rational ethics.

Key words: Pierre Abelard, ethics, will, actual sin, Christianity, intention.