Explanatory Gap

Conventional use of the term

In most of the existing literature, the following definition of explanatory gap is used:

Definition

$X$ exhibits an explanatory gap if $X$ cannot be derived logically from physical facts or physical theories. I.e., if it cannot be deduced.

Here, $X$ usually denotes a conception of phenomenal experience or a variation of qualia, and "physical facts" or "physical theories" refer to the physical broadly construed.

The problem with the above definition is that deductive forms of explanations are not the only forms of explanation in science. While deductive forms were first thought to be prevalent (most notably in Hempel's key article), philosophy of science has quickly realized that there are many other notions of explanation in use in science.

This point has been made particularly clear by (Elanor Taylor, 2015). She argues that explanatory gaps need to be studied relative to the different connotations of explanations that arguably are in use in science. Alternatively, it might be tempting to define an explanatory gap as in the next section.

Updated definition

Definition

There is an explanatory gap between a phenomenon $P$ and natural science if the phenomenon violates a necessary condition of all notions of explanation that are considered valid in science.

Hempel, Deductive Nomological Model of Explanation