Animal behavior (including that of insects) changes in reaction to pain, and not just while they're feeling it. They can be trained. They can remember pain, and act to avoid it in the future. In whatever sense they have knowledge, they know to avoid that. Pain is an awareness that you don't want to do something anymore, not an awareness of that awareness.
Buh? We can write systems with negative reinforcement. Say, a robot that performs various movements then releases a ball, detects how far from a target the ball landed, and executes this movement sequence less often if it was too far. I think "the robot avoids missing the target" is a fair description, and "the robot feels pain when it misses the target" is a completely bogus one. Do you disagree?
I ended up reading this article about animal suffering by this Christian apologist called William Craig. Forgive the source, please.
He continues the argument here.
How decent do you think this argument is? I don't know where to look to evaluate the core claim, as I know very little neuroscience myself. I'm quite concerned about animal suffering, and choose to be vegetarian largely on the basis of that concern. How much should my decision on that be affected by this argument?
EDIT: David_Gerard wins by doing the basic Google search that I neglected. It seems that the argument is flawed. Particularly, animals apart from primates have pre-frontal cortexes.