According to Derrida and taking inspiration from the work of Ferdinand de Saussure, language as a system of signs and words only has meaning because of the contrast between these signs. As Richard Rorty contends, "words have meaning only because of contrast-effects with other words...no word can acquire meaning in the way in which philosophers from Aristotle to Bertrand Russell have hoped it might—by being the unmediated expression of something non-linguistic (e.g., an emotion, a sensed observation, a physical object, an idea, a Platonic Form)". As a consequence, meaning is never present, but rather is deferred to other signs. Derrida refers to this—in his view, mistaken—belief there is a self-sufficient, non-deferred meaning as metaphysics of presence. A concept, then, must be understood in the context of its opposite: for example, the word "being" does not have meaning without contrast with the word "nothing".