  The second chapter, First Principles, lets the symbol 1 represent the Universe  “comprehending every conceivable class of objects, whether actually existing or not.” Capital letters \(X, Y, Z,\ldots\) denoted classes. Then, no doubt heavily influenced by his very successful work using algebraic techniques on differential operators, and consistent with De Morgan’s 1839 assertion that algebraists preferred interpreting symbols as operators, Boole introduced the elective symbol \(x\) corresponding to the class \(X\), the elective symbol \(y\) corresponding to \(Y\), etc. The elective symbols denoted elective operators—for example the elective operator red when applied to a class would elect (select) the red items in the class. 