It is interesting to observe, furthermore, that among the higher barbarians and civilized races, lust has become to a certain extent mentalized through hereditary memory and association.  Aristotle made a marvellous anticipation of modern scientific thought when he suggested that what made birds sing in spring was the memory of former seasons of love.  In men as in animals, the pleasant experiences of love and marriage become gradually ingrained in the brain, and when a youth reaches the age for love-making the memory of ancestral amorous experiences courses through his nerves vaguely but strongly.  He longs for something, he knows not what, and this mental longing is one of the earliest and strongest symptoms of love.  But it characterizes all sorts of love; it may accompany pure fancies of the sentimental lover, but it may also be a result of the lascivious imaginings and anticipations of sensualism.  It does not, therefore, in itself prove the presence of romantic love; a point on which I must place great emphasis, because certain primitive poems expressing a longing for an absent girl or man have been quoted as positive evidence of romantic love, when as a matter of fact there is nothing to prove that they may not have been inspired by mere sensual desires.  I shall cite and comment on these poems in later chapters.

Loss of sleep, loss of appetite, leanness, hollow eyes, groans, griefs, sadness, sighing, sobbing, alternating blushes and pallor, feverish or unequal pulse, suicidal impulses, are other symptoms occurring among such advanced nations as the Greeks and Hindoos and often accepted as evidence of true love; but since, like longing, they also accompany lust and other strong passions or violent emotions, they cannot be accepted as reliable symptoms of romantic love.  The only certain criteria of love are to be found in the manifestation of the altruistic factors—­sympathy, gallantry, and self-sacrificing affection.  Romantic love is, as I have remarked before, not merely an emotional phenomenon, but an active impulse. The true lover does not, like the sensualist and the sentimentalist, ululate his time away in dismal wailing about his bodily aches and tremors, woes and pallors, but lets his feelings expend themselves in multitudinous acts revealing his eagerness to immolate his personal pleasures on the altar of his idol.

It must not be supposed that sensual love is necessarily coarse and obscene.  An antique love-scene may in itself be proper and exquisitely poetic without rising to the sphere of romantic love; as when Theocritus declares:  “I ask not for the land of Pelops nor for talents of gold.  But under this rock will I sing, holding you in my arms, looking at the flocks feeding together toward the Sicilian Sea.”  A pretty picture; but what evidence is there in it of affection?  It is pleasant for a man to hold a girl in his arms while gazing at the Sicilian Sea, even though he does not love her any more than a thousand other girls.