On the Separability of Real and Financial Decisions.The financial manager faces two basic problems: first, the firm's investment or capital budgeting decision, and second, the financing decision. Capital investment and financing decisions are typically analyzed independently. Capital budgeting criteria proceeds under the simplest possible assumption about financing, namely all-equity financing. The only link between investment and financing decisions is the cost of capital. The basic idea behind Modigliani and Miller's famous proposition I is that in perfect markets, changes in capital structure do not affect value.