Including intangible capital significantly changes how we evaluate theories of investment. We show that including intangible capital in measures of investment and Tobin's q produces a stronger investment-q relation, especially in macroeconomic data and in firms that use more intangibles. These results lend support to the classic q theory of investment, and they call for the inclusion of intangible capital in proxies for firms' investment opportunities. However, including intangible capital also makes the investment-cash flow relation almost an order of magnitude stronger, which supports newer investment theories. The classic q theory performs better in settings with more intangible capital.