Aleph null is a cardinal number, and omega is an ordinal number. Both of them are infinite, and are the smallest infinite numbers of their respective type.
I don’t know about metaphysical infinity, obviously.
scienceblogs.com/goodmath/2008/10/infinity_is_not_a_number.php
First things first:
Infinity is not a number: please review the above url. Second, mathematics is based upon the unit. No matter what you consider, in regard to things mathematical, one must presuppose the unit, i.e., the number 1. Set theory is an exciting mind game. Yes, certain mathematical concepts can be proved by employing set theory, such as quantifying quantities. But, what is it’s relation to the real physical world? What matter do these concepts called “numbers”, whether in a set or not, inure to - and, especially as a “set”?
Number is nothing more than multitude measured by a unit. Multitude is the
genus of number, and the specific difference, that determines whether a number is this number or that number, is the final unit of the number in question. So, if I were to define two different multitudes of number, I would define them by their final number. In other words, the multitude called six (6) has as its final unit, six (6). The multitude called seven (7) has as its final unit, seven (7). If you vary the unit you vary the
species of number.
We also call numbers
discrete. Why? They are called discrete because each has an existence that is “discrete”. Two numbers, unlike two parts of a line which are continuous with another, have separate and independent existences. And,
multitude is different from
magnitude. Having just explained what multitude is, magnitude is continuous quantity. In other words, it is quantity having position. It is quantity of such things as the quantity of a line, or geometrical quantity.
If infinity is a
real number then infinity must also be
discrete. It must have its own independent and separate existence. It can’t be blurred and blended to be whatever one wants it to be. If “100,000,000,000,000,000,000,000,000,000,000,000,000,000,005” is an independent and separate number (that happens to be odd), it cannot be, “100,000,000,000,000,000,000,000,000,000,000,000,000,000,006”, or, “100,000,000,000,000,000,000,000,000,000,000,000,000,000,004”. It is no different with “infinity”. There cannot be an infinity that is “infinity + 1”, or an infinity that is “infinity - 1”, or, whatever we’d like it to be based upon our own exquisite whims. If it were, then I could argue that my infinity is larger (or, smaller) than your infinity. This would be absurd.
That is what is meant by
actual infinity. It speaks about infinity as a multitude of physical things in the real world, such as blades of grass or grains of sand. Now, if, on the other hand, we find ourselves with things such as grains of sand and we speak of them as
potentially infinite, we are acknowledging that the number of the grains of sand is increasing in the world due to erosion, etc., but, at this particular point in time, the current, actual number is finite. With each second of time that passes, another grain of sand is added to the pool of grains of sand on the earth. If I wait a year, then stop and ask, “Have we reached an infinity of grains of sand?” I must answer, “No.” And so on, year after year until the universe entropies.
Set theory is part of mathematics. It is not the entirity of it. And, it is certainly not the
principle of it. Arithmetic and mathematics does not flow from set theory.
jd