Synaethesia, both a neurological condition and literary trope, occurs when two of the traditional five senses are yoked together in a single sensory occurrence. In the strictest sense, synaesthesia in poetics, ?is a metaphorical expression in which the source and target domains represent concepts belonging to two different modalities or senses? (Shen 124). Emily Dickinson employs these types of expressions in poems such as ?I heard a Fly buzz ? when I died ?,? where in lines 12-13, ?There interposed a Fly ? / With Blue ? uncertain ? stumbling Buzz.? By synaesthesia, Dickinson suggests a narrator whose synergistic perception with the world eludes the five senses. Her complicating of sensory images reflects her understanding of experience, in which all elements of the physical and metaphysical fuse together under the single authorship of the self-referential poet. Much of the use of synaesthesia is informed by her concern with living experience in a manner which integrates all of her faculties. Maurice Merleau-Ponty?s writings on phenomenology recognize the ability of rhetorical synaesthesia to combine differing aspects of experience. He writes that, ?bringing the subtleties of experience to light and life requires extremely intentional, strategic acts of showing." Synaesthesia is the crux of this, because it has the ability to integrate all the senses, and symbiotically raise them above a purely physical experience. Emily Dickinson?s syanesthesia exemplifies how this literary device enacts the border of physical and metaphysical.