Our aim in this book is to reconstruct the historical development of an idea. This idea is the Content Theory of intentionality (CT for short).

By 'intentionality' we mean the ability of the human mind to refer to objects outside itself. To put it bluntly, our view is that all mental states that contain in themselves a "picture" of an external object are intentional. (In medieval Latin, the word intentio meant, among other things, picture or idea.) When I see a cat I have a "picture" of the cat in my mind; when I wish it wouldn't rain tomorrow I have in my mind a "picture" of tomorrow's unwelcome rain and so on.