Infinity symbol in bookbinding to indicate that a book is printed on acid-free paper and will therefore be long-lasting. In modern mysticism, the infinity symbol has become identified with a variation of the ouroboros, an ancient image of a snake eating its own tail that has also come to symbolize the infinite, and the ouroboros is sometimes drawn in figure-eight form to reflect this identification, rather than in its more traditional circular form. In the works of Vladimir Nabokov, including "The Gift" and "Pale Fire", the figure-eight shape is used symbolically to refer to the Möbius strip and the infinite, for instance
Actual infinity infinity in "Physics" and in "Metaphysics". He distinguished between "actual" and "potential" infinity. "Actual infinity" is completed and definite, and consists of infinitely many elements. "Potential infinity" is never complete: elements can be always added, but never infinitely many. Aristotle distinguished between infinity with respect to addition and division. "As an example of a potentially infinite series in respect to increase, one number can always be added after another in the series that starts 1,2,3... but the process of adding more and more numbers cannot be exhausted or completed." With respect to division, a potentially infinite sequence of divisions starts