Words, Thoughts and Theories argues that infants and children discover the
physical and psychological features of the world by a process akin to scien
tific inquiry, more or less as conceived by philosophers of science in the
1960s (the theory theory). This essay discusses some of the philosophical b
ackground to an alternative, more popular, "modular'' or "maturational'' ac
count of development, dismisses an array of philosophical objections to the
theory theory, suggests that the theory theory offers an undeveloped proje
ct for artificial intelligence, and, relying on recent psychological work o
n causation, offers suggestions about how principles of causal inference ma
y provide a developmental solution to the "frame problem''.