The skill, ingenuity, and knowledge of the forger and of those who exploit his work, are opposed to the skill, ingenuity, and knowledge of the collector and the learned world. The unaided human eye, if it has a trained and well-informed mind behind it, can go a long way in detecting forgeries. It is surprising how forgetful, careless, or ignorant a forger can be. He may employ materials whose inconsistency with the period to which his work claims to belong can be seen even by the unaided eye. More common is the introduction of such things as types and details of costume, or the use of coats of arms, that are later than the alleged date of the work. All such evidence, however, needs scrutiny, since it may simply be a case of later additions to a genuine object. More useful, therefore, may be tracking down the source of a forger’s borrowings. If, for example, these at first sight seem to come from an original work, but follow much more closely the variations from that original in a later copy or engraving, the conclusion is obvious. Again, investigation of pedigrees, checking of literary references, searching through exhibition records, may all reveal suspicious or occasionally damning evidence of falsified history. [Illustration: ABOVE: A forgery of a portrait by Cranach, and (BELOW) a genuine example. A style forgery, skillful, but coarser than an original.] [Illustration: (genuine example)] To tests based on observation and historical verification, we must add those mainly dependent on feeling. For the sensitive and trained observer, a number of indefinable characteristics will “add up” to a definite conviction of genuine or false. Qualities of surface and handling, subtleties in color and in the definition of form, the degree of unity in conception and treatment, and the emotional character of the work are among the things which influence such decisions. Thus, a copy, however exact, may reveal itself as lacking the coherence and the feeling which inspired the original; and the most skillful imitation of some older work may be recognized as a creation of its own time. Nobody can completely divorce himself from the prevailing thoughts, opinions, assumptions, feelings, and standards of his own period; and inevitably these will color whatever he produces, whether he be a forger or an original artist.