   As many philosophers are willing to recognize, the concept expressed by the word ‘consciousness’ is much in need of clarification. Three such clarifications are worth mentioning. Two of them consist in a pair of distinctions drawn by David Rosenthal (1986). One distinction is between creature consciousness and state consciousness. The other distinction is between transitive and intransitive consciousness. A creature can be said to be ‘intransitively’ conscious if she is alive and normally responsive to ongoing stimuli. She stops being intransitively conscious while in a dreamless sleep, if she is knocked out, drugged or comatose. A creature can be said to be ‘transitively’ conscious if she is conscious of things, properties and relations in her environment. Whereas a creature can be both intransitively conscious and transitively conscious of something, a mental state can only be intransitively conscious. One important aspect of the problem of consciousness is the problem of how to draw the line between conscious and unconscious mental states. A third clarification has been Ned Block’s (1995) distinction between access consciousness (or A-consciousness) and phenomenal consciousness (or P-consciousness). Whereas a state is said to be A-conscious if it is poised for free use in reasoning and for direct rational control of action and speech (i.e. available or accessible to several cognitive mechanisms), the P-consciousness of a state is what it is like to be in that state (whether or not it has A-consciousness). In recent work, Block (2007) has argued that much evidence from the cognitive scientific investigation of the visual system corroborates his distinction between P- and A-consciousness. For example, on his interpretation, experiments on change blindness and also the neuropsychological investigation of brain-lesioned human patients with neglect show that attention and working memory are necessary parts of A-consciousness, but not of P-consciousness. What makes a state A-conscious is that its content is made available to various cognitive systems (e.g., attention and memory). Furthermore, not unless a visual stimulus is attended and stored in working memory can an individual report having seen it. But Block (2007) takes the evidence to show that an individual can be P-conscious of the content of an unreportable stimulus, i.e. a stimulus whose content has not been either attended or stored in working memory. For supporting arguments, see Dretske (2004, 2007). Block’s interpretation of the cognitive scientific data has been criticized by scientific advocates of the so-called “global neuronal workspace model” of consciousness: see e.g., Dehaene et al. (2006) and Naccache and Dehaene (2007), which is a commentary to Block (2007). The global neuronal workspace model of consciousness nicely fits with Dennett’s (1991, 2005) position on intentionality and consciousness (which he has himself dubbed the “fame (in the brain) theory of consciousness.” (For further discussion of these issues, see the SEP entry on  attention.)