 Opposition to including references to traces in a philosophical theory of remembering often stems from particular conceptions of the nature of philosophical, as opposed to scientific, theories. Thus some have argued that philosophical theories of remembering should not posit traces on the ground that philosophical theories are or should be concerned with the nature of remembering as such, or perhaps with the concept of memory, whereas traces pertain to the mechanisms that, as a matter of contingent fact, underwrite the process of remembering (D. Locke 1971). One response to this argument maintains that the nature of remembering cannot be understood without understanding the mechanisms that underwrite the process of remembering (Sutton 1998). Another response maintains, more strongly, that traces may be part of the very concept of remembering (De Brigard 2014b; C.B. Martin &amp; Deutscher 1966).