Ruth Byrne's (Reference Byrne2005) book provides many examples of everyday imagination of variations on everyday experiences. Her focus on is the assessment of their rationality. In the cases that she (and the pertinent literature) discusses, the objects of the imagination are small variants on past events. Some of these variants are extreme ones and not very useful, such as imagining the probable but false event that my parents have never met each other. (This is how Clarence Darrow opens his autobiography.) Other variants are less imaginative but more useful, such as the options I could have taken that would have prevented me from getting stuck in a traffic jam. This may improve patterns of driving, and so it is eminently rational. Byrne observes that we do spend time and effort on such matters.

Byrne and the literature she refers to limit discussion to cases of imagination that vary only within a narrow compass of existing circumstances, and only within reason. One omission is that she does not discuss more extreme departures from reality, as in dreams or in daydreams. And so this book, like the rest of the literature to which it belongs, ignores Freud's theory of dreams and of daydreams, as well as the criticism of it and the alternatives to it. This is regrettable, since Freud offers a view of dreams as rational: Dreams give vent to our secret wishes and thus reduce our sense of frustration that can be debilitating. Moreover, dreams may be very pertinent to Byrne's concerns, as we often exhibit some patterns in normal thinking and in dreaming.

A second omission is developmental: Child psychologists show interest in the stages of cognitive development when children learn to realize the difference between experience and dreams or imaginations. Taking these stages seriously, we may see not only the growth of the sense of reality, but also the growth of the ability to think abstractly. These two directions of development diverge, and therefore we keep feeling the need to balance realism with abstractness and the freedom of imagination. This is why we need to check our sense of reality and keep our imagination in check. The writings of Ludwig Wittgenstein interest those who shun wild imagination; those of Karl Popper interest those who court it. Byrne's concern with the rationality of imagination may lead her to study this disparity.