Let us look, then, if possible, a little into this matter of Revolutions. Let us examine their facts, find out if possible their theory, and trace some leading outlines of their history keeping in view always the special relations of our investiga tions to the case of our own civil troubles. And it is no affecta tion to say, that when a man ventures to attempt such a theme, at such a time as this, it behooves him to gather all his best thoughts about him; to weigh well the theories he presents, and the judgments he renders; and to point the eye of inquiry and hope to that only which will not finally deceive. What, then, is Revolution? What is its definition? Tat its theory? What has been its history? When is it justifiable? When probably successful? These are questions which may indicate the general drift of inquiry which is before us.