Objective thought, as applied to the universe and not to phenomena, knows only alternative notions; starting from actual experience, it defines pure concepts which are mutually exclusive: the notion of extension, which is that of an absolute externality of one part to another, and the notion of thought which is that of a being wrapped up in himself; the notion of the vocal sign as a physical phenomenon arbitrarily linked to certain thoughts, and that of meaning as a thought entirely clear to itself; the notion of cause as a determining factor external to its effect, and that of reason as a law of intrinsic constitution of the phenomenon.