The exercise of mystical unknowing is central to the contemplative process prescribed in The Cloud of Unknowing. This thesis argues three distinct but interrelated claims about how unknowing works and what unknowing does in The Cloud of Unknowing. First, unknowing acts as the catalyst through which the process of apophasis begins. Unknowing also works as both a rhetorical device in the text and as apophasis in practice. Finally, unknowing functions as a preparation for the advancement of what The Cloud author calls the "blind stirring of love" which allows the contemplative potential access to oneness with God. This thesis is a rhetorical analysis of The Cloud that also engages discussions on epistemology and language to explain how and why knowing and knowledge are problematic for The Cloud author. This research is important because it may help expand the definition of knowledge, further the understanding of the implied category of non-discursive knowledge in contemplative literature, and broaden the understanding of what knowing means in both contemplative and non-contemplative contexts. This thesis also challenges the way we understand the human capacity to unknow and engage other forms of knowledge because The Cloud author works from an understanding that non-discursive knowledge exists and can be accessed by some humans.