 A fifth argument, related to the priority argument against the appeal to demonstrative concepts above, pertains to the possibility of concept acquisition or learning. Presumably what explains our coming to possess the observational concepts that we do is our undergoing appropriately related perceptual experiences (see, e.g., Peacocke 1992, 2001a, Ayers 2004). If this is so, it cannot be the case, on pain of circularity, that undergoing a particular perceptual experience depends on possessing the very concepts the acquisition of which the experience explain. Roskies (2008) argues that if we reject the claim that perception with nonconceptual content plays an essential role in concept acquisition, we cannot account for our acquisition of observational concepts without being committed to an unacceptable form of nativism. (See also Forman 2006 for a different argument purporting to show the necessity of perception with nonconceptual content to concept learning.)