The instrument for enforcing the law could be no other than public examinations, extending to all children, and beginning at an early age. An age might be fixed at which every child must be examined, to ascertain if he (or she) is able to read. If a child proves unable, the father, unless he has some sufficient ground of excuse, might be subjected to a moderate fine, to be worked out, if necessary, by his labour, and the child might be put to school at his expense. Once in every year the examination should be renewed, with a gradually extending range of subjects, so as to make the universal acquisition, and what is more, retention, of a certain minimum of general knowledge, virtually compulsory. Beyond that minimum, there should be voluntary examinations on all subjects, at which all who come up to a certain standard of proficiency might claim a certificate. To prevent the State from exercising, through these arrangements, an improper influence over opinion, the knowledge required for passing an examination (beyond the merely instrumental parts of knowledge, such as languages and their use) should, even in the higher class of examinations, be confined to facts and positive science exclusively.