Are we so sure that plants aren't sentient or can't be sentient? We originally assumed we were the only sentient and self aware animal on the planet. We've gradually realized that we're definitely not, but the assumption that self-awareness and sentience must look similar to what it does in us seems to have stuck.
Think about what's required for pavlov's experiment. They took pea plants and turned on, by turns, a fan and a light from one of two opposite directions. In the control group, there was no correlation between when they turned on the fan and when they turned on the light. In the experimental group, they consistently turned on the fan an hour or two before they turned on the light.
Pea plants will grow towards light pretty actively. In the experimental group, they would consistently grow in the direction of the fan - expecting the light to follow the wind.
Think about what's required for that. You have to be able to sense your environment. You have to have an awareness of light and wind. And you have to be able to associate the presence of wind - something that normally has nothing to do with the presence or absence of light - with the later coming of the light.
That pretty strongly suggests there's some level of sentience at work here.
My point isn't to say "Don't eat plants." It's to question whether eating other sentient beings is really avoidable for us as autotrophs. And if it is unavoidable, where does that leave us ethically?
For me, it leaves me trying to treat everything I eat with care and respect and an awareness that my life comes at the cost of other lives.
And then primarily examining the health and sustainability impacts of my diet, rather than using an incomplete ethics.
