Fundamentally, William Shakespeares Sonnet 146 is a poem about overcoming Death. The primary metaphor of the poem represents a war between body and soul, by which one defeats Deathvia the physical bodyin order to achieve eternal life. Thus the war is twofold, taking place both in physical and spiritual terms. The word "Foiled" describes both aspects of this struggle: in the physical sense, "to foil" is "to overthrow, defeat, or baffle" (OED); in addition, "foiled" signifies "to foul, pollute, or violate the chastity of" (OED), a definition which arouses a sense of spiritual defilement. Furthermore, in the poems shift from this metaphor of warfare to the ownership of a house, the word "foiled" speaks directly to the material nature of the body as a finite structure which encapsulates, or houses, the soul.
In the opening stanza, Shakespeare uses the metaphor of physical warfare to emphasize the level of opposition between body and soul. The soul is foiled"oppressed" or "pressed hard upon" (OED 3) by the body so that its position in "the centre" is clearly to be pitied: "Poor soul, centre of my sinful earth" (ln. 1). Furthermore, the language suggests that the soul not only dwells within the body but is also its prisoner or victim. It is captive to the bodys "rebel powers" (2) while internally stifled: "Why dost thou pine within and suffer dearth" (3). Thus the soul is in a "foiled" position: it is frustrated, baffled, thwarted. The use of the word "rebel" confirms the fact that the bodyas a mutinous poweris waging an attack with intent "to overthrow, defeat, or inflict a foil upon" (OED II.4) the soul. Similarly, the word "array" in its original context suggests this sense of physical warfare as it is "to put on (dress, armour, etc.)" (OED 4b) as well as "to draw up prepared for battle" (OED 1).
Just as "to foil" implies external warfare it likewise reflects spiritual defilement. As the soul seeks to regain control of the body, the body aims "to foul, defile, or pollute" the soul. Thus its primary motive is "to dishonour, or violate the chastity of" (OED 5.III) the soul. In a more literal sense, "to foil" also implies "to cause, or drop excrement" (OED 8).
Corresponding to this sense of defilement, the term "foil" relates to the concept of the body as a transient packaging which encases the soul. Shakespeare emphasizes this idea by using a register of words whose imagery is loosely focused around the ownership of a house, or, the process of acquiring and maintaining a place of residence. As a metaphor, the "fading mansion" (ln.6) of the body, with its "short lease" (ln.5), is essentially a temporary covering for the soul. In the same way, as a noun, a foil is "a thin layer (of any material), a leaf (of a plant), or a leaf (of paper)" (OED 3.b). Furthermore, a "foil" is "used as a wrapping, or container" just as the body, with its "outward walls" (ln.3) is regarded as a vesselor wrappingfor the soul.
In essence, the body is seeking "to prevent the success of" (OED 5) the soul in achieving immortality by purchasing "terms divine" (ln.11). Based on the variety of contexts in which the term may be applied, it is clear that the "Poor soul" is none other than "Foiled by" the "rebel powers" (ln.1-2) with which it paradoxically adorns itself.