Combinatorics was introduced by Ramsey to solve a special case of the decision problem for the **first-order** predicate calculus.

According to it, sky blue would be the blue of the **first order** in Newton's scale.

The light scattered from small particles is of a much richer blue than the blue of the **first order** as reflected from a very thin plate.

He was a master printer and an artist of the **first order**.

For a single quantic of the **first order** (ab) is the symbol of a function of the coefficients which vanishes identically; thus (ab) =a1b2-a2bl= aw l -a1ao=0 and, indeed, from a remark made above we see that (ab) remains unchanged by interchange of a and b; but (ab), = -(ba), and these two facts necessitate (ab) = o.