 Although each of these philosophers have tended to frame it in a way that reflects their other theoretical commitments, some version of the idea that attention is always involved in the making of epistemic moves can be made pre-theoretically plausible. The inattentional blindness experiments, in which participants are visually presented with large changes while attending to something else, show that inattentive people can fail to notice all sorts of perceivable things that attentive people would find obvious. Something exactly similar seems to be true in the case of a priori reasoning: just as no item is so large, so central, and so well-lit that no conscious and sighted observer could miss it, so there is no step in reasoning that is so simple, so compelling, and so obvious, that every thinker, whether attentive or inattentive, can be expected to recognise it. Just as the inattentional blindness effects might seem to show that there are attentional demands that a thinker has to meet before his perceptual encounter with things can provide him with knowledge of them, so it is plausible that there are similar attentional demands that have to be met before the thinker’s grasp of a thought gives her a justified belief in that thought’s consequences. This interpretation of the inattentional blindness effects is, however, controversial. Nicholas Silins and Susanna Siegel have suggested that – even if inattention does sometimes explain a perceiving person’s failure to form a belief about the things happening in their visual field – unattended aspects of experience are nonetheless capable of providing justification for such beliefs (Silins and Sigel, 2019). Émile Thalbard argues to the contrary (Thalabard, 2020).