 However it is important to understand that Worrall’s repeated expression of his position in terms of the heuristic conception of novelty (particularly after his 1985) does not amount to an endorsement of strong heuristic predictivism. Worrall clarifies this in his 1989 article that focuses on the evidential significance of the ‘white spot’ confirmation of Fresnel’s version of the wave theory of light. The reason the white spot datum carried such important weight is not ultimately that it was not used by Fresnel in the construction of the theory but because this datum followed naturally from the core theory that light is a wave. The reason the fringe data that was used to compute the wavelength of sodium light (cf. above) did not carry such weight is that it is not a consequence of this core idea (nor has the wavelength of sodium light been fixed by some other data). Thus d is novel for T when “there is a heuristic path to [T] that does not presuppose [d’s] existence” (Scerri &amp; Worrall 2001: 418). As Worrall sometimes puts it, whether d carries unconditional confirmation for T does not depend on whether d was actually used in constructing T, but whether it was ‘needed’ to construct T (e.g., 1989: 149–151). Thus Worrall is actually a proponent of ‘essential use-novelty’ (Alai 2014: 304). For Worrall, facts about heuristic prediction and accommodation serve to track underlying facts about the logical relationship between theory and evidence. Thus Worrall is ultimately a proponent of weak (not strong) heuristic predictivism. Worrall categorically rejects temporal predictivism, arguing that the fact that the white spot was a temporally novel consequence in itself was of no epistemic importance. 