Definition.com
Apathy is, for the Stoics, the extinction of the passions by the ascendency of reason.
Definition.com
Apathy is the condition of a person who has sat on the fence for so long that the iron has entered into his soul.
Definition.com
Apathy can be overcome by enthusiasm, and enthusiasm can only be aroused by two things: First, an ideal, with takes the imagination by storm, and second, a definite intelligible plan for carrying that ideal into practice.