The attempt to form a just conception of the value of work done in any
department of human knowledge, and of its significance as an indication
of the intellectual and moral qualities of which it was the product,
is an undertaking which must always be beset with difficulties, and may
easily end in making the limitations of the appraiser more obvious
than the true worth of that which he appraises. For the judgment of a
contemporary is liable to be obscured by intellectual incompatibilities
and warped by personal antagonisms; while the critic of a later
generation, though he may escape the influence of these sources of
error, is often ignorant, or forgetful, of the conditions under which
the labours of his predecessors have been carried on. He is prone to
lose sight of the fact that without their clearing of the ground and
rough-hewing of the foundation-stones, the stately edifice of later
builders could not have been erected.