> Most legumes have a pretty high carb-to-protein ratio, and are also incomplete proteins.
This is a red herring, based on misinformation about nutrition. It is not hard to fulfill your daily protein needs and get in all your essential amino acids and maintain a healthy calorie intake while eating a diet of legumes, grains, and vegetables. It can be done for a fraction of the price of a omnivore's diet and can be a lot better nutritionally than downing tuna every day (i.e., there's more opportunities for variety).
> there's probably no reasonable definition of sentience that includes all animals and excludes all plants.
There are a few, but it actually is largely irrelevant. If you stop eating animals you also consume less plants. Every time you eat an animal you have to consider that in order to raise that animal it had to eat a lot of plants that you could've been eating instead. Raising animals is massively inefficient energy-wise, which is why our plant consumption goes down when people stop eating meat.
So really there's no need to draw a "sentience line" in the sand. Assuming everything is sentient, vegetarian diets are better for both plants and animals. But even if it were necessary to draw this sort of line, it would make a fair deal of sense to say that anything without a nervous system is at least relatively less likely to be sentient. There are some arguments for plant sentience due to their limited molecular signalling responses to harmful stimuli, but there is definitely a lot less evidence to support that hypothesis than there is to support the hypothesis that tuna are sentient.
It sounds to me like you've decided that some species matter more than others based on your own arbitrary perceptions rather than rational or empirical reasoning. It's okay to kill a cow but not a dolphin. Why? Is that just because you've taken your own beliefs as ground truth and reasoned your way from there?
Consciousness is poorly defined, so I don't know exactly what you're getting at there, but one definition is sentience. At any rate, I believe it's fair to say that a sentient being can be described as conscious due to their ability to feel and subjectively process experiences.
Why does consciousness matter if you believe they are sentient? Are you perhaps conflating intelligence with consciousness? Do you believe that it matters more when an intelligent animal suffers than it does when a less intelligent animal suffers? Why? Do they not both suffer? Can the same be said for people with low IQs? Their suffering matters less than mine?
How do you reconcile that slaughterhouse conditions are torturous, even the ones that "ethical farmers" use? That we have video footage that indicate the animals know they are going to die and evidence to suggest the entire process is distressing and painful? That the process by which they are "humanely" anaesthetized/killed (e.g., bolt gun) is still by far not the most humane way to kill animals?
How about the fact we have every reason to believe pigs are incredibly intelligent despite the way we treat them (I'm talking Chimpanzee-level intelligence here — http://animalstudiesrepository.org/cgi/viewcontent.cgi?artic...)? What is this "thing" you believe separates them from dolphins?
Are you sure you are not simply working off of your own unchallenged beliefs that you were raised with by your parents and taking those as ground truth?
Mmm just for the record if you look at neuroscientific and cognitive science evidence it's actually a pretty safe bet that all of those marine creatures are sentient... intelligence and the capacity to feel are pretty separate.
We can't be absolutely sure that anyone except for ourselves suffer (not even other humans) because of the other minds problem, but essentially all the scientific evidence we have suggests that humans and other creatures are sentient if they have basic nervous systems and begin to display behaviors consistent with suffering.
Some of my sources: Studied neuro and cog sci myself, just chatted last night with a PhD candidate in neuro who agrees with me, have taken classes with the former longstanding editor of Brain and Behavioral Science who I believe would also agree. There are cog sci journals out there dedicated to this stuff.
But that's not factually true. Take your pick of most legumes. They're cheaper, have more than enough protein as well as other nutrients, are more environmentally sustainable and don't require killing sentient creatures...
This is a red herring, based on misinformation about nutrition. It is not hard to fulfill your daily protein needs and get in all your essential amino acids and maintain a healthy calorie intake while eating a diet of legumes, grains, and vegetables. It can be done for a fraction of the price of a omnivore's diet and can be a lot better nutritionally than downing tuna every day (i.e., there's more opportunities for variety).
> there's probably no reasonable definition of sentience that includes all animals and excludes all plants.
There are a few, but it actually is largely irrelevant. If you stop eating animals you also consume less plants. Every time you eat an animal you have to consider that in order to raise that animal it had to eat a lot of plants that you could've been eating instead. Raising animals is massively inefficient energy-wise, which is why our plant consumption goes down when people stop eating meat.
So really there's no need to draw a "sentience line" in the sand. Assuming everything is sentient, vegetarian diets are better for both plants and animals. But even if it were necessary to draw this sort of line, it would make a fair deal of sense to say that anything without a nervous system is at least relatively less likely to be sentient. There are some arguments for plant sentience due to their limited molecular signalling responses to harmful stimuli, but there is definitely a lot less evidence to support that hypothesis than there is to support the hypothesis that tuna are sentient.