This is an answer to Name That Trait which asks what trait differentiates humans from animals. The named trait should justify vegan-objectionable activities such as slaughtering animals for food.
Short answer: the trait is being a universal knowledge creator. This answer relies on lots of non-standard background knowledge such as The Beginning of Infinity.
This post gives a different argument which I think is easier to understand with less background knowledge. It will still require going over some background.
The Problem of Design
An important problem in the history of philosophy is the problem of design, famously argued by William Paley. It says some objects (such as an animal or pocket watch) have the appearance of design which requires explanation. Paley’s explanation was that a pocket watch has an intelligent, human designer, and animals were designed by God.
Plants, animals and pocket watches have the appearance of design. They’re complex. Stones, crystals, dirt and stars don’t. This is a big difference. Stones and stars are worth explaining in terms of fundamental physics like the big bang, but plants merit additional explanation. Plants e.g. have chloroplasts which do photosynthesis, which are nothing like rocks and wouldn’t be created randomly or purposelessly.
The above is widely accepted. What’s not widely known is that “appearance of design” is knowledge. Knowledge is information adapted to a purpose.
The underlying problem is how knowledge can be created starting with non-knowledge. Where can new knowledge come from? How can it originate?
This is a hard problem and not many answers have been proposed. The bad answers include magic, knowledge is just created sometimes out of thin air, and designers. Saying that a designer created the knowledge doesn’t explain how the designer created the knowledge (using intelligence – but how does intelligence work?), nor where that designer’s intelligence came from. If you say knowledge comes from God who already has tons of knowledge, then where did God come from?
A single good answer has been developed. It’s the only known answer that makes much sense. It’s the theory of evolution. Replication with variation and selection is able to adapt information to a purpose and thereby create new knowledge. The appearance of design, in plants and animals, was created by evolution.
Where did eyes come from? Evolution. Why does a rabbit run away from danger? It evolved to do that. Why are trees structured in an organized way with the leaves on top where they can better receive light? Because that structure has better survival and replication value for trees (survival and replication value is the short answer for what biological evolution selects for). Etc. This is widely accepted.
With this background in mind:
How does intelligence work and create new knowledge? I believe intelligence works by evolution, literally, not as an analogy. (Seriously I find that 90% of people assume I mean an analogy even though I just told them I didn’t.) This is not a mainstream view. It’s been developed by Critical Rationalist philosophers, especially David Deutsch.
Biological evolution does replication with variation and selection of genes. Intellectual evolution does replication with variation and selection of ideas. Genes and ideas are both things which it’s possible to make copies of – replicators – so evolution applies to them.
FYI, the view that evolution applies to replicators is a fairly standard view in the field even though most of the public is ignorant of it. It’s held by e.g. Richard Dawkins and is why he developed the idea of a “meme” (which means an idea that replicates). A meme plays the role in the evolution of ideas that a gene plays in the evolution of plants and animals.
Name That Trait
Lots of animal behavior has the appearance of design (or the appearance of intelligence or purposefulness). This indicates knowledge is involved. I think that knowledge comes from the animal’s genes and was created by biological evolution. I think it’s this appearance of intelligent behavior that is the primary reason people (correctly) differentiate animals from rocks.
Human behavior also has the appearance of design, so what’s the difference? Humans create new knowledge that isn’t in their genes. Instead of relying only on biological evolution for knowledge, humans do intelligent evolution of ideas within their minds. This is a capacity that no animal has and explains why only humans were able to invent philosophy and science.
When an animal does intelligent-appearing behavior, the designer was biological evolution. When a human does intelligent-appearing behavior, the designer is usually a human being who created ideas using mental evolution of ideas.
Animals have one source of knowlege: genetic evolution. Humans have two sources of knowledge: genetic and memetic evolution.
People commonly assume that the appearance of design in animal behavior is an indicator of intelligence, while the appearance of design in an animal’s eyes and claws is not. The primary mechanism by which genes control animal behavior is through creating the animal’s brain according to a design detailed in the animal’s genes. The animal brain is a computer which the genes build and configure with behavioral algorithms. Humans work differently because they’re capable of doing evolution within their minds to create new algorithms, new behaviors, new ideas. etc.
Getting from these claims to a full case against animal welfare or rights requires additional arguments. I won’t detail them here but see this post for some explanation. The basic issue is that animals aren’t differentiated from rocks in a relevant way because genes (which are where the knowledge is) are not conscious and can’t suffer (like rocks), and animals behave according to algorithms in conceptually the same way as a robot like a self-driving car.