Third, we might ask Hume to be clearer in his distinctions. For instance, are dream images impressions or ideas? Most likely they are ideas, since they consist of a mixture of imagination and memory. However, dreams are (arguably) phenomenally indistinguishable from waking experience: we cannot prove that we are dreaming from within a dream. Thus, all our impressions from within a dream are as real to us as we dream them as waking impressions are to us when we experience them.