Conceptually, cardiac contractility is the potential for contraction that cardiac muscle possesses by virtue of the physicochemical environment of the muscle cell, e.g., calcium handling and contractile proteins. It is what the muscle (heart) is capable of doing. The search for simple indices of contractility has been an attempt to provide an operational definition of contractility. However, none of the simple indices that have been proposed has been particularly robust, and all have either been abandoned or used with less than originally anticipated enthusiasm. This should not be particularly surprising for two reasons: First, the regulated cardiac pump is not simple. Where the heart functions at any point in the range of the multitude of possibilities available to it will depend on many factors. In addition, requiring simplicity not only flies in the face of the reality of cardiac performance, it almost guarantees that important characteristics of cardiac performance will be excluded from the assessment of contractility. Two, a corollary of the “simplicity” requirement is that an index must also be “loadindependent”. This requirement derives from a recognition of the complexity of cardiac performance--for a simple index to be useful in describing the essential character of a complexly regulated cardiac pump, the complexity either has to be accounted for or not allowed to express itself by holding constant all other factors. The “load-independence” requirement is an attempt to do the latter. However, this requirement also is unrealistic because properties of cardiac muscle that we would view as part of “contractility” are inextricably linked to rate and load (e.g., intervalforce behavior and length-dependent activation). Thus, given the complexity of the regulated cardiac pump, the multiple interacting determinants of cardiac performance, and the marvelous adaptive ability of cardiac muscle, it is not surprising that a robust, simple load-independent index has not been found. For these same reasons, continued searching for a simple index of contractility is likely to be as un-satisfying in the future as it has been in the past. Rather, the complexity of the regulation of cardiac performance begs for a broader view of contractility that includes the complexity in a quantitative multivariate approach that acknowledges the real way the system functions, is regulated, and adapts.