We always try to use old memories to recollect how we solved problems in the past. But nothing's ever twice the same, so recollections rarely match. Then we must force our memories to fit — so we can see those different things as similar. To do this, we can either modify a memory or change how we represent the present scene. For example, suppose you need a hammer but can only find a stone. One way to turn that stone to your purposes would be to make it fit your memory of a hammer's appearance — for example, by making your description of the stone include an imaginary boundary that divides it into two parts, to serve as handle and as head. Another way would be to make your hammer frame accept the entire stone as a hammer without a handle. Either scheme will make the memory match the description, but both will lead to conflicts in other agencies.
How hard it will be to make such a match depends both on which agents are now active in your mind and on the levels of their priorities — in short, upon the context already established. It will be easy for you to see two things as similar when you only need to change relatively weak attachments at the conceptual fringes of familiar things. But frequently the ease of comprehension will also depend upon how readily you can switch from one mental realm to another.
Consider what must happen in our minds when poets speak about their loves in romantic, floral terms. We all have learned a certain common way to represent a woman's beauty in terms of flowers that are prone, alas, to fade. For centuries this formula has been established in our language and literature; however, at first it must have seemed bizarre. We cannot possibly match our descriptions of women and flowers if we insist on interpreting such phrases and poems literally — that is to say, illiterately — entirely within the physical realm of the appearance, composition, and behavior of a typical flower.
To be sure, the colors, symmetries, and smells of flowers can certainly arouse the sorts of states we associate with things we've come to see as beautiful. But the more essential trick is in knowing how to turn entirely away from the physical realm and dwell instead upon the images and fantasies that flowers evoke in other spheres — such as the sense of a thing so sweet and innocent, so helpless and delicate, that it invites affection, nurture, and protection. Features like these must be made to fit the listener's private love ideal — only then can the metaphor match.
This, Herrick's bitter verse defeats. By holding us so tightly to the usual frames for human shapes, he steers us into fantasies of vegetables with hands and feet.