If you don't understand consciousness, how to make it from first principles and how it works, then I don't think you can confidently say "this isn't conscious" about much.
We don't need to lean on consciousness nor other mysteries at all. Nor we do have to when a rock changes color as it gets wet.
And without this parsimony, then we could claim that any unexplained mystery underlies any well-understood phenomenon which doesn't sound like much of an epistemic standard.
Ultimately it's a bit of an inprecise human concept. The boundaries of what fits in there might be somewhat unclear, but we definitely things that intuitively are (humans) and aren't (plants, rocks) in this set.
But if I cut myself, no amount of science can currently assess how much pain I feel or how much it bothers me.
You can observe that a human and a record player can both say "hello", but you can not make the argument from that that there is no way to disprove that a record player might wish to express a greeting to a fellow being.
A simple process can duplicate the outward appearance and effect of a complex one (an mp3 player can talk), and a complex process can duplicate the outward appearance and effect of a simple one (a human can crank a drive shaft), and neither of these means that one might just as well be the other. They don't mean anything at all by themselves either for proving or disproving.
Humans reacting to stimuli in largely similar ways to a plant, or even plain physical process like water filling a vessel or diffusion, neither proves nor disproves, nor even merely implies or suggests, nor even merely opens any doors to any room for doubts about anything.
It could be that there is no fundamental difference between a human and a plant and a toaster, but this observation about similar behavior provides nothing towards the argument.
Perhaps "consciousness" is just a poor term to use in a scientific discussion.
The same for a plant; if you cut it, science won't tell you how much pain it feels, or how much it's bothered by your act of violence.
If we're going to agree on anything, I just wish consciousness discussions could agree on some phenomenological referent(s) for the term "consciousness". The word is used in a way that is little more than a sed-replace for elan vital, regaling all discourse to little more than a volley of solipsistic value proclamations IMHO.
mr jc-bose explored exactly these ideas more than a century ago !
Isn't the capability of dreaming and simulating situations in your head the definition of consciousness?
Plenty of AIs are capable of something very much alike to "dreaming and simulating situations in your head" too. Humans really hate the idea of AIs being conscious, so surely that means dreaming can't be in any way important for determining whether something is conscious or not.
I find some irony in the mention of elan vital upthread - on the one hand, most people here wouldn't let themselves be caught dead believing in elan vital, but then switch to any thread discussing AI, or even cognition in animals (or plants, like here), and suddenly vitalism becomes the mainstream position once again.