Actual infinity vs. potentially infinity - Math philosophy

In summary: The difference between "actual infinity" and "potential infinity" is that actual infinity includes all numbers that can be expressed as (potentially) infinite decimal expansions, while potential infinity includes all numbers that can be expressed as (potentially) infinite rational expansions. Actual infinity is greater than potential infinity because it includes more numbers.
  • #1
highmath
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what the differences between actual infinity to potentially infinity?
 
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  • #2
Have you searched for this? I get a wiki-article, some articles (scholarly and otherwise) and a few videos that claim to provide explanations.
(For example, to my relief, I just learned from this that I apparently side with the majority of mathematicians that "accept actual infinities".)

If you have a more specific question, I am quite sure there are more capable people here to answer it.

Note: I think one of the confusions that often appears in such discussions, is that people oppose the actually infinite on the grounds of limitations imposed by physical reality. This is not correct: Rather, the discussion does not depend on physical, but philosophical and foundational constraints.
 
  • #3
Janssens said:
Have you searched for this? I get a wiki-article, some articles (scholarly and otherwise) and a few videos that claim to provide explanations.
(For example, to my relief, I just learned from this that I apparently side with the majority of mathematicians that "accept actual infinities".)

If you have a more specific question, I am quite sure there are more capable people here to answer it.

Note: I think one of the confusions that often appears in such discussions, is that people oppose the actually infinite on the grounds of limitations imposed by physical reality. This is not correct: Rather, the discussion does not depend on physical, but philosophical and foundational constraints.
I don't understand the bold and underline texts.
Can you explain it?
 
  • #4
highmath said:
I don't understand the bold and underline texts.
Can you explain it?

Physical quantities such as mass and velocity have a finite magnitude. (In the case of velocity, there is even a particular upper bound.) However, this is not relevant in the context of "actual vs. potential infinity", because in that context we are concerned with sets as abstract mathematical structures, not as representations of the values of physical quantities.
 
  • #5
I find a quote from Dedekind somewhat apropos: "If space has at all a real existence it is not necessary for it to be continuous; ... And if we knew for certain that space was discontinuous there would be nothing to prevent us, in case we so desired, from filling up its gaps, in thought, and thus making it continuous;"

Dedekind, "Continuity and Irrational Numbers" in "Essays On the Theory of Numbers"; translation by Wooster Woodruff Beman.
 

FAQ: Actual infinity vs. potentially infinity - Math philosophy

What is the difference between actual infinity and potentially infinity?

Actual infinity refers to a state where a quantity or set is considered to have an infinite amount of elements or values. Potentially infinity, on the other hand, refers to a concept where a quantity or set has the potential to be infinite, but is not currently so.

How is the concept of infinity relevant to mathematics?

Infinity is a fundamental concept in mathematics, as it allows for the representation and manipulation of quantities and sets that are too large or too small to be comprehended or measured in a finite way. It is used in various mathematical fields, such as calculus, geometry, and number theory.

Can actual infinity exist in the physical world?

This is a highly debated topic in philosophy and mathematics. Some argue that actual infinity can exist in the abstract realm of mathematics, but cannot be observed or proven in the physical world. Others believe that actual infinity can manifest in the physical world through concepts such as the infinite divisibility of matter.

What is the controversy surrounding the concept of infinity?

The controversy surrounding infinity stems from its paradoxical nature. For example, some argue that if actual infinity exists, then it must contain all possible elements or values, including contradictory ones. This leads to questions about the logical consistency of infinity and its implications for mathematics and the philosophy of knowledge.

How does potential infinity relate to the concept of limits in mathematics?

Potential infinity is often used in the concept of limits, where a quantity or set approaches infinity but does not actually reach it. This allows for the representation and calculation of values that are infinitely large or small, but still within a finite range of measurement or understanding.

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