Plants are not sentient. What do you mean by "meant"?
Not that we know of now, but that can change in the future, plats may be sentient (I do not think so personally) but I am open for the possibility.
Sure, but we can only work within known science. All sorts of things that we haven't figured out yet can potentially be true, but taking such unknowns into account would be irrational.
We need to take the fact that we do not know into account at least. Just as it was not uncommon to view animals as non-sentient for sure in the past. We have no way of actually ->
-> measuring sentience, but we infer the likelihood from comparing the biology of humans and animals. But yeah, we have no clue about how consciousness works.
We can acknowledge the fact that we don't know everything, but we can't act based on things we don't know. Science or even doing anything rational would be impossible under such logic.
Science is a method that works great in some fields of life, but what gets funded, prioritized and is used as argumentation in human affairs are also subject to politics and economics.
Science isn't perfect, I agree.
The great thing with science (Scientific Method) over time is that it can only get better results over time, the special part is that it updates and discards mistakes systematically.
