Life is defined by Maturana and Varela as a type of self-organization: autopoiesis in the physical space. This resembles the concept of metabolism, which itself is typically included in definitions of life. Three senses of metabolism are distinguished. If life depends on either autopoiesis or metabolism (in the third sense), then strong A-Life is impossible. The theory of autopoiesis challenges concepts familiar in biology and cognitive science. While its use of informational language is too restrictive, its use of cognitive language is too liberal: life does not imply cognition.