One way in which the theme of dreams is evident in The Effect of Gamma Rays on Man-in-the-Moon Marigoldsis in how there must be a commitment to one's aspirations that transcend one's present state of being in the world.  Ruth, Tillie, and Beatrice are shown to have dreams.  Yet, how they navigate their hopes and aspirations for the future within the present tense is the defining element in their pursuits.  Zindel seems to be suggesting that if individuals wish to make their dreams come true, they can only do so through a faith that transcends the conditions of the external world.  For example, Beatrice has hopes for her life improving through the desire to open a tea shop or becoming a dancer.  Yet, Beatrice cannot overcome the cruelty that exists the world.  In the process, she becomes a victim of it, and her dreams wither because of it.  Ruth is so trapped by the perceptions of others and how she appears to other people that she is fundamentally incapable of nurturing her dreams in a manner that allows her to pursue them.  

Zindel argues that Tillie is the only one whose dreams will materialize.  While Tillie endures much from the world around her and even the people within her world, she does not sacrifice her dreams.  She does not take the form of the world around her, and this quality is what will enable her dreams to materialize.  Zindel feels that dreams can become reality if individuals are able to believe in them with so much authenticity and pure love that they are able to repel the world around them.  When individuals love their dreams selflessly, like Tillie, there is a greater chance their hopes will become realized.