Oh, no, not that annoying dictionary atheist argument again!

From Pharyngula

Once upon a time, there was a man who thought rather highly of humanity's potential. Sure, there were things humans did that were awful -- they could be violent, and careless, and short-sighted -- but they also did amazing things like science and art that other species didn't. Overall, he thought that calling someone "human" was a high compliment. And this idea colored his thinking in such a way that it began to shape his expectations of people; maybe we should expect human beings to do more than eat and excrete and reproduce, and maybe we should recognize that the word "human" meant an awful lot more than just a certain flavor of meat or the species of your parents.

He also noticed that every single human being he ever met, without exception, was more than a perambulating set of chromosomes. Some were good at math and others liked to dance and others were kind and yet others liked to argue, and these were the virtues that made them good and interesting, and made them…human, in this best sense of the word. So when he praised being human, it wasn't for the accident of their birth, it was for the qualities that made being human meaningful.

Unfortunately, not all humans liked having the fact that words carry greater connotations than the most narrow, most literal, most concise, dictionary-style definitions, despite the obvious fact that they all do. They got quite irate.

"I am a human because I am not a squirrel, or a hyena, or a fish, or broccoli," some said, "and I resent the fact that you think there's more to me than being a not-squirrel!"

"You expect me to be good at math to qualify as human?" complained some of the slower, less alert people, who failed to notice that the man had made no such specific requirements.

"The only thing that all humans have in common is that they were born to other humans, and can only reproduce with humans," said other complainers, "therefore, that is all that 'human' can imply or mean. How dare you taint my pure and perfect language with complications and nuances and expectations!" 

And the man listened to their arguments for a while, and argued back for a while, and then he came upon a simple solution. He told the not-squirrels and identity-by-rutters and functional illiterates and simple-minded machine-coders to fuck off, and it was good.

"Ad hominem!" they squeaked.

"Who cares what barely human people think, anyway," he shrugged.