The ideas about "Newton polygons" subsume Eisenstein's criterion, and are set up to be applied in a straightforward way to polynomials over Dedekind rings, e.g., number fields. For given ideal in the base ring, graph the convex-upward hull of the ords of the coefficients at that ideal. The (negative) slopes of the resulting line segments are the ords of the roots, with respect to the extension(s) of the ord on the groundfield, with multiplicities (=the length of the segment with given slope). Thus, if there is a single line segment with slope $m/n$ (in lowest terms) and $n$ is the degree, the polynomial is irreducible. A straightforward argument (modulo basic algebraic number theory) is visible on-line at <