 Predicted evidence for Worrall is thus evidence that is not used to fix free parameters. Worrall cites two forms that predictions can take: one is when a particular evidential consequence falls ‘immediately out of the core’, i.e., is a consequence of the core, together with ‘natural auxiliaries’, and the other is when it is a consequence of a specific version of a theory whose free parameters have been fixed using other data. To illustrate the first: retrograde  motion[11]  was a natural consequence of the Copernican core (the claim that the earth and planets orbit the sun) because observation of the planets was carried out on a moving observatory that periodically passed other planets—however it could only be accommodated by Ptolemaic astronomy by proposing and adjusting auxiliary hypotheses that supposed the planet to move on an epicycle (retrograde motion did not follow naturally from the Ptolemaic core idea that the Sun, stars and planets orbit the earth). Thus retrograde motion was predicted by the Copernican theory and thus offered unconditional support to that theory, while it offered only conditional confirmation to the Ptolemaic theory. The second form of prediction is one which follows from a specific version of a theory but was not used to fix a parameter—imagine \(W'\) in the preceding paragraph makes a new prediction p (say for another experiment, such as the one slit experiment)—p offers unconditional confirmation of \(W'\) (and W; Worrall 2002: 203).