 Corporate finance concerns the financing of firms. One question concerns a firm’s capital structure: should a firm obtain funding through equity (that is, from shareholders expecting dividends) or through debt (that is, from bondholders who lend money to the firm and have a contractual right to receive interest on the loans), or through a combination of the two. A key result in corporate finance is the Modigliani-Miller theorem, which says that a firm’s capital structure is irrelevant to its market value (Modigliani &amp; Miller 1958). This theorem makes a number of highly unrealistic assumptions, among them the assumption that markets are efficient, and that there are no taxes. Alongside many other results in economics, it may therefore be considered as useless for predictive purposes; or even as dangerous, once used for such purposes nonetheless (Egidi 2014). In a detailed study of the Modigliani-Miller theorem, Hindriks (2008) has argued, however, that the value of highly idealized models in economics may lie in their providing counterfactual insights, just as in physics. Galileo’s law of free fall tells us what happens in a vacuum. Despite the fact that vacuum is rare in reality, the law is not uninformative, because it allows us to associate observed phenomena to the extent to which an unrealistic assumption must be relaxed. Similarly, if one of the assumptions that the Modigliani-Miller theorem makes is the absence of taxes, the observed relevance of capital structure may well have to be explained as resulting from particular tax regimes. The explanation obtained by relaxing unrealistic assumptions is called “explanation by concretization” (Hindriks 2008).