hrm. i'm reminded of john locke. he tackled the problem of whether we could think of things that we hadn't yet experienced. he thought that there were atomic (basic) experiences and we could only obtain those via experience. what hte mind could do was to rearrange those atomic (basic) experiences in novel ways.

one example... we experience a horse... and we experience an animal with a horn... then we blend those elements together in novel ways in order to produce something we have never experienced (a unicorn). or the torso of a man and the body of a horse to make a centaur, or stuff like that.

but really... he thought the elements of experience were such things as colour (could you have the idea of red without having never experienced red? he thought you needed the experience on order to acquire the idea in order to put red someplace novel e.g., by using ones imagination to come up with the idea of a red person or whatever).

i'm not sure how much you can dream something that you haven't experienced. i guess i figure there are some ideas (aka concepts) that can only be acquired via experience (or can only be grasped in certain ways via experience) but that once we have those concepts then we can blend them in all kinds of novel ways... i dreamed i could flap my arms and fly but i've never ever experienced that. i have experienced swimming, however, and my kind of flying is basically 'swimming' in the air where i have to work hard to stay 6 feet in the air as one has to work hard to stay submerged in water...