The teaching of Algebra in the early stages ought to consist of a gradual generalisation of Arithmetic; in other words, Algebra ought, in the first instance to be taught as

Preface to

Every mathematical book that is worth reading must be read "backwards and forwards," if I may use the expression. I would modify Lagrange's advice a little and say, "Go on, but often return to strengthen your faith." When you come to a hard or dreary passage, pass it over; and come back to it after you have seen its importance or found the need for it further on.

*Algebra*