It’s France. 1881. Sunny day. Tepid, but sunny. You are Pasteur. You are famous. You are the Académie. The Académie is everything. Let’s talk anthrax.

Sheep are moneymakers. But anthrax kills them. You’ve got a theory about that. If anthrax is alive, then you can beat it up. If you made a vaccine, using oxygen to weaken anthrax spores—that’s the key, you weaken one version, beat them up; then give that to the sheep; then they don’t get the stronger version for real—then you’d be the moneymaker. You have a biological theory, is what we say. You can attenuate live microbes. I don’t really know what that means, but you do. You are Pasteur.

Now you are someone else. Someone we’ve never heard of: Toussaint. You know what? You are not in the Académie, you mustachioed veterinarian. Your chemical theory of anthrax is unimpressive. You think antiseptics will work for attenuation. Which means you disagree with Pasteur. Just dab some carbolic acid—that’s an antiseptic, different ball game than oxygen—into the old anthrax; vaccinate the sheep. Since disease is a chemical problem, contra biological, you can sit back and await your invite to the Académie. You’re going to the show. You just created the world’s first successful artificial anthrax vaccine. Remember, farm animals are everything. The nation, the soul, the air in the croissant. You saved them.

But wait. You are not Pasteur.

Now we’re back to the sunny day. And this is Pasteur again. Hippolyte Rossignol has challenged you to prove yourself at his Pouilly-le-Fort farm. You can’t make up names like those. This has to be true. He says: you vaccinate my sheep, then a month later we’ll give them anthrax, then you’ll come back a few days after and we’ll see if this works. You agree, aware that this will confirm your greatness.

One problem though—Toussaint. Your lab tests are making you skeptical about the biological theory. You hear this upstart Toussaint got some good numbers with antiseptics, with the chemical theory. Ever toggling between brazen self-confidence (here, the debunker of spontaneous generation; the heater, but not boiler!, of milk) and seething self-awareness (I am who I am, am I not? I know these things to be true, yet if not?), you do what it takes. Staring at the floor, you kick some dust, take a deep breath, and set up the public experiment. No more comme çi comme ça, this is huge.

You take twenty-five sheep. You lead the spectators to believe your vaccine is the fantastic oxygen-attenuated. Remember: that’s biological. Milk, fermentation, potato blight, it’s all biological. With Hippolyte looking over your shoulder— “we’re not so different, you and I” —you inject. Thing is—it’s not oxy-atten. It’s antiseptic-atten. Oops. You’re not using your famous Je suis le Pasteur theory. Thing is, too: not just that you’re bailing on your bio-theory and using Toussaint’s chem-theory. Also, you took that antiseptic-atten and washed it through mice three times. What does that mean? Means you’re on the sly, that things are going on behind the scenes that belie the forthcoming public triumph. But I still don’t get it, you confess? Okay, me neither. But there’s some kind of deception going on is the important thing. Your milk fame is fun, sure, but how long can it pay the bills? You can digress just this once. It’s a detour, this biological shucking. A blip on the screen. You’ll win the day. Look in the mirror. Psyche yourself up.

You come back two weeks later. You inject again. Again, using the Toussaint tactic. Two weeks later—inject the real deal, the actual anthrax. Now it’s tense. Will they live? Will it work? Pressure cooker, pins and needles, gnawed fingernails. Or so we’d assume. Except you have a guy on the inside, stethoscope to the door, at Pouilly-le-Fort. Things will be fine. The boys at Comptes Rendus will love this stuff. You are Pasteur.

June 2. It’s time. Take the train from Paris out to Pouilly-le-Fort. Step off the train to fanfare, actual newspaper reporters, high-school band, international coverage fanfare. Are the sheep alive? Will you still be Pasteur? Will they know you used Toussaint’s technique and rigged the trial?

Just tell me this: anyone ever heard of Toussaint? Je suis Pasteur, he says. Je suis indeed.