We also can't know "for certain" that a rock isn't screaming silently, or that there isn't a china teapot orbiting the sun between Earth and Mars. Science doesn't deal in absolute certainties; it deals in probabilities based on evidence. There is zero evidence for plant consciousness and massive evidence against it.

Consciousness, as far as we observe it in the entire animal kingdom, is an emergent property of a centralized nervous system processing information. Plants lack neurons, a brain, or any substrate capable of integrating information into a unified experience.

Claiming a plant might be conscious is like claiming a calculator might be running Call of Duty. It’s not that we "don't know", it's that the hardware simply cannot run that software.

Evolutionarily, consciousness (and specifically the ability to feel pain or fear) is a mechanism to trigger escape or avoidance. Since plants are sessile (they cannot move), developing a complex, energy-expensive system to "feel" damage would be a massive evolutionary disadvantage. Why would nature select for an organism that can feel being eaten but do absolutely nothing about it?