 Frege would also read \(R^{+}(x,y)\) as: \(x\) is a member of the R-series ending with \(y\). Logicians call \(R^{+}\) the ‘weak-ancestral’ of \(R\) because it is a weakened version of \(R^*\). When we define the natural numbers below, and take \(R\) to be precedes, we can intuitively regard its weak ancestral, precedes\(^{+}\), as the relation less-than-or-equal-to on the natural numbers. 