IV.  The Laws of Plato contain numerous passages which closely resemble other passages in his writings.  And at first sight a suspicion arises that the repetition shows the unequal hand of the imitator.  For why should a writer say over again, in a more imperfect form, what he had already said in his most finished style and manner?  And yet it may be urged on the other side that an author whose original powers are beginning to decay will be very liable to repeat himself, as in conversation, so in books.  He may have forgotten what he had written before; he may be unconscious of the decline of his own powers.  Hence arises a question of great interest, bearing on the genuineness of ancient writers.  Is there any criterion by which we can distinguish the genuine resemblance from the spurious, or, in other words, the repetition of a thought or passage by an author himself from the appropriation of it by another?  The question has, perhaps, never been fully discussed; and, though a real one, does not admit of a precise answer.  A few general considerations on the subject may be offered:—­

(a) Is the difference such as might be expected to arise at different times of life or under different circumstances?—­There would be nothing surprising in a writer, as he grew older, losing something of his own originality, and falling more and more under the spirit of his age.  ’What a genius I had when I wrote that book!’ was the pathetic exclamation of a famous English author, when in old age he chanced to take up one of his early works.  There would be nothing surprising again in his losing somewhat of his powers of expression, and becoming less capable of framing language into a harmonious whole.  There would also be a strong presumption that if the variation of style was uniform, it was attributable to some natural cause, and not to the arts of the imitator.  The inferiority might be the result of feebleness and of want of activity of mind.  But the natural weakness of a great author would commonly be different from the artificial weakness of an imitator; it would be continuous and uniform.  The latter would be apt to fill his work with irregular patches, sometimes taken verbally from the writings of the author whom he personated, but rarely acquiring his spirit.  His imitation would be obvious, irregular, superficial.  The patches of purple would be easily detected among his threadbare and tattered garments.  He would rarely take the pains to put the same thought into other words.  There were many forgeries in English literature which attained a considerable degree of success 50 or 100 years ago; but it is doubtful whether attempts such as these could now escape detection, if there were any writings of the same author or of the same age to be compared with them.  And ancient forgers were much less skilful than modern; they were far from being masters in the art of deception, and had rarely any motive for being so.