A young man is a theory, an old man is a fact. E. W. Howe

A young man is a theory, an old man is a fact.

Democracy is beautiful in theory; in practice it is a fallacy. Benito Mussolini

Democracy is beautiful in theory; in practice it is a fallacy.

Maxwell's theory is Maxwell's system of equations. Heinrich Hertz

Maxwell's theory is Maxwell's system of equations.

The theory of Communism may be summed up in one sentence: Abolish all private property. Karl Marx

The theory of Communism may be summed up in one sentence: Abolish all private property.

One of my teachers, Jack Ratcliffe, who had given an excellent course on electromagnetic theory during my final undergraduate year. Antony Hewish

One of my teachers, Jack Ratcliffe, who had given an excellent course on electromagnetic theory during my final undergraduate year.

If the theory of relativity had also been necessary for salvation, it would have been revealed to Saint Paul or to Moses. Georges LemaĆ®tre

If the theory of relativity had also been necessary for salvation, it would have been revealed to Saint Paul or to Moses.

The theory of evolution, like the theory of gravity, is a scientific fact. Neil deGrasse Tyson

The theory of evolution, like the theory of gravity, is a scientific fact.

The Newton of drift theory has not yet appeared. His absence need cause no anxiety; the theory is still young and still often treated with suspicion. Alfred Wegener

The Newton of drift theory has not yet appeared. His absence need cause no anxiety; the theory is still young and still often treated with suspicion.

The theory of Probable Evidence is the mathematical contribution to Logic, and is of paramount importance. Alexander Bain

The theory of Probable Evidence is the mathematical contribution to Logic, and is of paramount importance.

A mathematical theory is not to be considered complete until you have made it so clear that you can explain it to the first man whom you meet on the street. David Hilbert

A mathematical theory is not to be considered complete until you have made it so clear that you can explain it to the first man whom you meet on the street.

In 1975, ... [speaking with Shiing Shen Chern], I told him I had finally learned ... the beauty of fiber-bundle theory and the profound Chern-Weil theorem. Chen-Ning Yang

In 1975, ... [speaking with Shiing Shen Chern], I told him I had finally learned ... the beauty of fiber-bundle theory and the profound Chern-Weil theorem.

Mathematics is the queen of sciences and number theory is the queen of mathematics. Carl Friedrich Gauss

Mathematics is the queen of sciences and number theory is the queen of mathematics.