I don't agree that "it implies that certain principles of logic are not invariant." I'm claiming that the definition of "human" is invariant, bound by the contents of all curent human knowledge. I'm saying that new knowledge (the extsitence of rational alien beings) would require a new definition or a new word. What principle of logic does this make variant? I'm saying that if you extend the definition of the word "human" to include rational alieng beings as well as rational human beings, why can't you just change the definition of the word "atom" to include everything, since that would still be "consistent across the largest set of all possibles." The key for a definition is the essential characteristics (the Conceptual Common Denominator).
According to whom? Lets take the word atom, it's been around for about three thousand years. The ancient Greeks used it to be mean that which is indivisible. Today, atoms are indeed divisible, so we stop calling modern atoms their namesake? So, by your logic atoms are not atoms, yet they are. Paradox/Contradiction! Whoops!
So, that pretty much proves my point. Just because a word was once attributed to a single definition does not imply it is that way forever, nor that knowledge modifies, condenses, and expands the lexicon. In short, words too are subject to the CCD, in that when a word becomes to mean another thing it gets changed over and the older definition is depreciated.
I think their definition of "human being" is not quite right, because an upright stance and articulate speech are not a distinguishing feature of humans ("upright" is subjective and surely other animals could be considered to have an upright stance; and some animals communicate within their breed via articulate speech, like dolphins) and because it suggests that humans' ability to reason is merely a faculty that any animal has and can develop (like if a dog developed mentally to a point at which we considered them "superior" then it would be human). But I agree that a distinguishing and essential characteristic of human beings is that they must be "a man, woman, or child of the species Homo sapiens." This would simply not include aliens.
No, aliens would be called persons too since they are rational agents. You seem to be going in circles here. Where is Person defined in philosophy in general to solely and wholly mean humans? Not a single time have I seen such a definition, not by Rand and not by her contemporaries, nor ours.
My stance is unchanged; I think the word "human" would not include rational aliens or robots should we discover/invent them; instead, I think that a new word would be coined to define the new creature, as well as another new word to encompass both (or all rational beings, even unknown ones).
Human != Person, please try again. You're going in circles!
Here's your logic.
A) A human is a person because of XYZ properties. In this case, the property of REASON and volition are the primary features that define a person. And humans have these qualities, so they're PERSONS.
B) You're ASSUMING because all we know is humans in the category of PERSONS, that THERE CAN BE NO OTHER SPECIES IN THE GENUS PERSONS. That doesn't follow, you have not shown a conclusive logic proof or an empirical basis for that any rational volitional agent organic, in-organic, or whatever cannot be a person. I have proven my case by the fact that the MAJORITY OF PHILOSOPHERS AGREE that PERSONS is a GENUS for which HUMANS ARE A SUBSET BUT *NOT* THE SET THEREOF. Therefore, the onus is now on you to show why this relationship between PERSONS and HUMAN is wrong.
My argument still stands, and you have yet to knock it down. Get to work and stop the circling. If I wanted circling I'll read Leonard Peikoff.
-- Bridget