In the relatively new academic fields of Horror Theory and Monster Theory , Mary Douglas's 1966 classic "Purity and Danger" is frequently evoked.
In the ancient academic field of penicillin studies, Douglas's Big Idea has never been braced ---- until now.
Her stunningly original thesis was that "dirt" is merely 'order out of place' : that we believe that gardening soil 'belongs' strictly in the garden field and everything is in order while it remains there.
It can never properly belong among the bed sheets.
Pure (that is , in the right place only) gardening soil is not intrinsically dirty, impure or dangerous - just as bed sheets, on beds, are equally pure and 'in order' .
But have either item leave the mental box we have inserted them into and danger, dirt and impurity quickly emerges.
They are now dynamically fluid hybrids - fused beings - a little garden soil and a little bed sheet with much of our fear coming from the uncertainty over just how much the fused creature is of each.
Douglas also does discuss the opposite of fusion - fission.
This is when a normally solid dry complete object (say a living body) becomes a dynamically uncertain mixture of part solid dry normal body and part mold-dissolved gooey wet decaying nothingness.
This produces another hybrid that crosses mental borders - with the living being solid, dry and complete - while the decayed dead is wet , dissolving and incomplete.
Something similar happens early on when as children we realize that the cooked whole fish, still biologically complete and detailed , will later emerge from us as just a pile of shapeless gooey feces.
This putrefaction of a single being, for all of us, is as least as disgusting and disturbing as any fused being.
Physically, we the living are totally unharmed by the fact that penicillium threads will soon weave their way through the dead body of our beloved in their coffin.
But mentally, that image shakes us to our core.
And that image and dozens like it centring on our revulsion to molds crippled our use of natural penicillin for twenty years : from 1928 to 1948.
Quite quickly, after only a few weeks work in 1928, it was shown that natural penicillium mold juice was both harmless and a great lifesaver.
Rather like oranges are to scurvy threatened sailors on the seas for a long time - a small amount of active Vitamin C buried in a tasty impure mixture of dozens of others of non-toxic materials.
But for about twenty wasted years, Normal science and scientists/doctors ( including the man who first determined it was perfectly safe - Alexander Fleming !) absolutely refused to save the lives of the dying.
Not if that meant having to accept the use of natural - impure - penicillium juice inside the temple of the human body.
Rationally they claimed to accepted the 1928 evidence as a scientific fact (and they were never able to disprove it) --- but emotionally they could not.
"Impurity IS Danger" was their unconscious mantra - and they consciously found ways to rationalize this emotional response into excuses as why they declined to use natural penicillin to save the dying.
Hippocrates weep !