The sentence “All people are equal.” (and ones like it) seems simple at first glance but actually contains a lot of depth. Depending on how you interpret it, it can be false or subjective, but I don’t think it’s true.
The most naive interpretation is obviously false. All people are literally not equal in the physical sense. Our atoms are in different configurations. Neither are we equal in the psychological sense. We react to the same stimuli in different ways.
So what in the world do people mean when they say all people are equal?
Do they mean everyone has equal rights? That makes a little more sense, but it is not true. I do not have the same rights as someone living in Switzerland or China.
Hmm, maybe they mean that everyone has equal opportunities? A quick thought falsifies this interpretation. So what do they mean???
What someone really means when they say “All people are equal.” is “I wish for all people to be equal!” which is neither true nor false. It is a wish about the future. I do wish for all people to be equal (but not in the Harrison Bergeron sense, more along the lines of equal rights).
The reason we knee-jerk react to “All people are equal.” is because our culture has conditioned us, from the humanism of the Enlightenment to the Declaration of Independence and onwards, to believe it is true. We don’t realize that we are really stating a wish when we think we are making a true statement, and this is dangerous.
Conversely, there are some statements that look like opinions (or maybe even falsehoods) at first glance, but are actually true. (Statements about intelligence fit this category very nicely, but I’m going to leave them out.) These statements usually go against what culture has conditioned us to believe. For example: “All people are not equal.” This statement is true but is usually interpreted as “I wish for all people to have unequal rights.” (a wish), but it should just be interpreted as a fact. Again, this is dangerous, since it masks what is really true.
In order to push society forward – to actually make everyone equal and become better – we need to separate our beliefs and wishes. If we believe that something that is not true (but that we want to be true) is actually true, we won’t notice it as much and will not spend as much time and effort on fixing it. If, however, we could accurately believe the (sometimes inconvenient) truth, we could reduce the time until our wishes become the truth.
Now go fix the world!
I think most people view "All people are equal" as a pronouncement of a moral belief they hold, not as a statement of fact. When they say, "All people are equal", they mean they believe "all people should be treated equally", or "everyone should have to obey the same laws" or "everyone's needs have equal importance".
This moral pronouncement is also consistent with a utilitarian pronouncing "All people are equal to me", as in that all people's lives hold equal weight in his utility function.
This is a point of disagreement, for me, then. It holds if you start from a premise that "rights" are things granted by laws and governments. Or, I guess, a premise that "rights" are "claims about what I should be allowed to do that I can reliably trust to hold in practice in my local environment." It does not hold if, like many Enlightenment philosophers, you start from a premise that rights are things humans have automatically (either from God, or because there's no prohibitions against them in a state of nature, for example). In this model governments and laws can protect, preserve, or infringe on rights, but not grant them. This is why the US Bill of Rights has only negative rights (restrictions on government power) and no positive ones.