This theme seems like a heavy-hitter, what with the big "ism" and all, but existentialism really boils down to a school of thought based on the idea of existence itself—not existence in our minds, but our living, breathing selves. In "Design," Frost examines life as he finds it in the physical world and wonders about all the big questions: Why are we here? Where did we come from? Were we made this way? Those aren't exactly multiple choice, kids.
Frost is right on the edge of two extremes (and we don't mean a couple of these guys). Either the world is random and meaningless, or it is planned-out and harshly cruel.
Our physical existence confirms what we already knew: appalling things happen and humans simply have to live in the midst of it. Tough jerky, gang.
We're big on freedom, sure, but everything has its limits. For thousands of years, humans have taken comfort in the idea that, while we might make our own choices, someone or something is still in ultimate control of the universe. We like the idea that not everything is just coincidence. It makes us feel like there's a good reason (even if we can't grasp it) why we missed our bus and got splashed by a passing truck in the process. But in "Design," Frost sees the scary side of that idea. If a creator is in control, that means that this god must have a hand in everything, including all the terrible stuff. It's not just saving kittens, after all.
Frost is clearly outraged that God would meddle in the tiny affairs of the world in such a violent way. Harumph.
The dark underside to the poem is the word "IF"—it is entirely possible that everything is random coincidence and we are here on our own. Yipe.
"Design" isn't a ghost story. Really nothing all that awful happens. A spider gets ready to eat a moth. It's the circle of life—get over it. But the philosophical argument that Frost develops begins to play with some of our deepest fears. Frost moves from telling a story to asking questions, questions that become increasingly more urgent. It is as if he is slowly uncovering all the possible implications of the scene and he is terrified of what he discovers. And we're quaking in our loafers right along with him. (What? Don't hate—they were a Christmas gift.)
Frost works hard to make us fear this little scene by associating it with everything that makes us afraid—death, disease, spiders, even witches. (We're glad he left out heights.)
Frost argues that God doesn't just control everything that happens in the universe; he rigs the whole thing just to freak us out. (Thanks a lot, big fella.)
In "Design" there's a lot of supernatural stuff going on. We've got the big guns of the supernatural world: God and the cosmic forces that control our lives. But we also have the small potatoes of the other-worldly realm—witches, overweight spiders, and pale flowers. The whole poem is about big things and small things and whether those big and small things are controlled by superstition, by God, or (hang on to your hackey-sacks) even by nothing at all.
The first stanza refers only to small superstitions (the spider, the heal-all, the witches' broth), but Frost takes his supernatural discussions to a cosmic level by the end of the poem. Far out, Frosty.
Even though Frost makes plenty of references to the supernatural, at the end of the poem we still aren't sure whether he even believes that anything supernatural exists.