From a philosophical point of view you may well be correct. However, there is the option of using behavioural observations as a surrogate. For example, exposing living things to pain stimuli and analogising the response to what we humans know to be a typical reaction to pain.

This does carry the risk of inappropriately anthropomorphising non-human species, but as the question of whether other creatures feel pain is intimately linked to the morality of how humans should treat them (after all, we're not going to be able to stop other animals from inflicting pain on each other), then maybe it's not a problem.

I have a microcontroller, a tiny DC motor, a pair of wheels, and a handful of thermistors. From these I build a robot, autonomous to the limit of its battery charge, which senses the temperature of its surroundings and acts on this information to move itself toward temperatures within a range its programming defines as preferable. The speed with which it does so is determined, to the limit of the motor's capability, by the difference between the temperature it's moving away from, and the temperature it's moving toward.

If I use a cigarette lighter or a lit match to apply an open flame to one of this robot's thermistors, it will flinch away from the stimulus as fast as it can. This is closely analogous to "what we humans know to be a typical reaction to pain"; if you applied the same stimulus to one of my fingers, after all, I would initially react in much the same fashion.

From this behavioral observation, do you conclude that my robot's subjective experience a) exists at all, and b) encompasses the experience of pain? Does this behavioral observation inform your concept of the morality surrounding how this robot is treated by humans? Why, or why not?

You raise a good counterpoint. Perhaps it's less to do with analogy and more to do with empathy. Which is again a subjective appraisal of the topic.

... but your robot isn't delicious...

Not to us, because we don't eat rocks and metal. If there's a planet out there whose apex predator species is silicaceous in the same way we're carbonaceous, then, there, my robot is halfway to being a cricket, and is probably quite tasty when properly prepared.

(I eagerly invite speculation on what, on our notional silicaceous Earth-analog, might constitute a parallel to veganism.)

Only eating Apple. Drrump, tissch!

Next time you're in the DC/Baltimore area, look me up! In exchange for a laugh like that, the least I can do is buy you a beer.

Hmmm, next time you're in Bonnie Scotland you can buy me one ;-)

Many of the most important concepts in science, not to mention ethics, are not yet well defined... I don't think your stance here is very productive.