In this contribution a logical analysis is given of the in design research regularly held expert position to prescribe expert design practices as favourable de-sign practices to other designers. First I argue that despite its conservative starting point to consider only types of already existing expert design practices as favourable, the position allows for some room to also prescribe new types of design practices. Second, I analyse the very claim that expert design practices define types of favourable practices. It is shown that the expert position may be formulated in a way in which this claim is tautological, and in a way in which it involves empirical prediction. This latter formulation allows testing the expert position by determining whether designers when mimicking experts indeed engage in favourable design practices.