Our first inquiry respects the meaning of the term Liberty as distinguished from that of Necessity. These terms do not differ, as expressing genus and species; that is, Liberty does not designate a species of which Necessity expresses the genus. On the other hand, they differ by way of _opposition_. All correct definitions of terms thus related, will possess these two characteristics. 1. They will mutually exclude each other that is, what is affirmed of one, will, in reality, be denied of the other. 2. They will be so defined as to be universal in their application. The terms _right_ and _wrong_, for example, thus differ from each other. In the light of all correct definitions of these terms, it will be seen with perfect distinctness, 1st, that to affirm of an action that it is right, is equivalent to an affirmation that it is not wrong; and to affirm that it is wrong, is to affirm that it is not right; 2d, that all moral actions, actual and conceivable, must be either right or wrong. So of all other terms thus related. The meaning of the terms Liberty and Necessity, as distinguished the one from the other, may be designated by a reference to two relations perfectly distinct and opposite, which may be supposed to exist between an _antecedent_ and its _consequent_. 1. The antecedent being given, one, and only one, consequent can possibly arise, and that consequent _must_ arise. This relation we designate by the term Necessity. I place my finger, for example, constituted as my physical system now is, in the flame of a burning candle, and hold it there for a given time. The two substances in contact is the antecedent. The feeling of intense pain which succeeds is the consequent. Now such is universally believed to be the correlation between the nature of these substances, that under the circumstances supposed, but one consequent can possibly arise, and that consequent must arise; to wit--the feeling of pain referred to. The relation between such an antecedent and its consequent, therefore, we, in all instances, designate by the term Necessity. When the relation of Necessity is pre-supposed, in the presence of a new consequent, we affirm absolutely that of a new antecedent. 2. The second relation is this. The antecedent being given, either of two or more consequents is equally possible, and therefore, when one consequent does arise, we affirm that either of the others might have arisen in its stead. When this relation is pre-supposed, from the appearance of a new consequent, we do not necessarily affirm the presence of a new antecedent. This relation we designate by the term Liberty. CHARACTERISTICS OF THE ABOVE DEFINITIONS. On the above definitions I remark: 1. That they mutually exclude each other. To predicate Liberty of any phenomenon is to affirm that it is not necessary. To predicate Necessity of it, is equivalent to an affirmation that it is not free.