# Hilbert 2nd problem

In his 1990 lecture to the International Congress of Mathematicians in Paris, David Hilbert presented a list of open problems in mathematics. He expressed the 2nd of these problems, known variously as the *compatibility of the arithmetical axioms* and the *consistency of arithmetic,* as follows:

- When we are engaged in investigating the foundations of a science, we must set up a system of axioms which contains an exact and complete description of the relations subsisting between the elementary ideas of that science. The axioms so set up are at the same time the definitions of those elementary ideas; and no statement within the realm of the science whose foundation we are testing is held to be correct unless it can be derived from those axioms by means of a finite number of logical steps. Upon closer consideration the question arises:
*Whether, in any way, certain statements of single axioms depend upon one another, and whether the axioms may not therefore contain certain parts in common, which must be isolated if one wishes to arrive at a system of axioms that shall be altogether independent of one another.*

- When we are engaged in investigating the foundations of a science, we must set up a system of axioms which contains an exact and complete description of the relations subsisting between the elementary ideas of that science. The axioms so set up are at the same time the definitions of those elementary ideas; and no statement within the realm of the science whose foundation we are testing is held to be correct unless it can be derived from those axioms by means of a finite number of logical steps. Upon closer consideration the question arises:

- But above all I wish to designate the following as the most important among the numerous questions which can be asked with regard to the axioms:
*To prove that they are not contradictory, that is, that a definite number of logical steps based upon them can never lead to contradictory results.*

- But above all I wish to designate the following as the most important among the numerous questions which can be asked with regard to the axioms:

This problem is said by some to have been solved, albeit in a negative sense, by K. Gödel (see Hilbert problems and Gödel incompleteness theorem).

And yet, in his 2000 Distinguished Lecture to the Carnegie Mellon University School of Computer Science, Gregory Chaitin began his remarks as follows:

- I’d like to make the outrageous claim, that has a little bit of truth, that actually all of this that’s happening now with the computer taking over the world, the digitalization of our society, of information in human society, you could say in a way is the result of a philosophical question that was raised by David Hilbert at the beginning of the century.

The philosophical question to which Chaitin was referring is the surmise at the heart of Hilbert’s 2nd problem.

Chaitin titled his lecture “A Century of Controversy Over the Foundations of Mathematics.” This article presents a brief history of this ongoing controversy.

## References

- Hilbert problems,
*Encyclopedia of Mathematics*.

- Hilbert, D. "Mathematische Probleme" Nachr. K. Ges. Wiss. Göttingen, Math.-Phys. Klasse (Göttinger Nachrichten) , 3 (1900) pp. 253–297 (Reprint: Archiv Math. Physik 3:1 (1901), 44-63; 213-237; also: Gesammelte Abh., dritter Band, Chelsea, 1965, pp. 290-329) Zbl 31.0068.03, URL: https://www.math.uni-bielefeld.de/~kersten/hilbert/rede.html, Accessed: 2015/06/03.

- Hilbert, D. "Mathematical problems" Bull. Amer. Math. Soc. , 8 (1902) pp. 437–479, MR1557926 Zbl 33.0976.07, URL: http://aleph0.clarku.edu/~djoyce/hilbert/problems.html, Accessed: 2015/06/03.

- Chaitin, G, “A Century of Controversy Over the Foundations of Mathematics,“ Journal Complexity -- Special Issue: Limits in mathematics and physics, Volume 5, Issue 5, May-June 2000, pp. 12-21, (Originally published in
*Finite Versus Infinite: Contributions to an Eternal Dilemma*, Calude, C. S.; Paun, G. (eds.); Springer-Verlag, London, 2000, pp. 75–100), URL: http://www-personal.umich.edu/~twod/sof/assignments/chaitin.pdf Accessed 2015/05/30.

**How to Cite This Entry:**

Hilbert 2nd problem.

*Encyclopedia of Mathematics.*URL: http://encyclopediaofmath.org/index.php?title=Hilbert_2nd_problem&oldid=36442