The theory of business finance in a modern sense starts with the Modigliani and Miller (1958)
capital structure irrelevance proposition. Before them, there was no generally accepted theory of
capital structure. Modigliani and Miller start by assuming that the firm has a particular set of
expected cash flows. When the firm chooses a certain proportion of debt and equity to finance its
assets, all that it does is to divide up the cash flows among investors. Investors and firms are
assumed to have equal access to financial markets, which allows for homemade leverage. The
investor can create any leverage that was wanted but not offered, or the investor can get rid of
any leverage that the firm took on but was not wanted. As a result, the leverage of the firm has no
effect on the market value of the firm.