In our day-to-day lives we are aware of many different things, from the taste of the coffee we just drank to our own hopes and dreams. The central aim of my project is to understand such awareness. I begin by considering awareness of external items, and argue that representation of an external object is necessary, but not sufficient, for awareness of that object. It is commonly supposed that in order to get a sufficient condition for awareness, the representation of the object must be cognitively accessed by the subject. I give two arguments against this view. The 'content mismatch' argument and the 'capacity mismatch' argument. I argue that cognitive accessibility can allow for both a content and capacity match with external awareness, and develop a plausible neural mechanism underlying cognitive accessibility. I then extend this theory to account for awareness of mental states. I argue for a nonrepresentational theory where the difference between internal and external awareness depends on what is attended. Finally, I develop a theory of visual attention. I argue that attention is a tool as it is used by subjects to do things. In particular, I argue that attention functions similarly to a highlighter in that they both have the function of making the selected target stand out from the surrounding items. I then ground this theory of attention in neural mechanisms distributed throughout the brain.