This episode features Stuart Ritchie, intelligence researcher and author of the book "Intelligence: All That Matters." Stuart responds to some of the most common conceptual objections to the science of IQ testing. Can we even define intelligence? Aren't there lots of different kinds of intelligence? How do we know the tests are measuring intelligence at all instead of something like motivation or familiarity with the style of testing? Does it undermine the meaningfulness of IQ as a metric that people can improve over time, with practice, or over generations?