Furthermore, Epicureanism provided a view of nature which was apt in the minds of an imaginative poet to lead toward romanticism.  Stoicism indeed pretended to be pantheistic, and Wordsworth has demonstrated the value to romanticism of that attitude.  But to the clear of vision Stoicism immediately took from nature with one hand what it had given with the other.  Invariably, its rule of “follow nature” had to be defined in terms that proved its distrust of what the world called nature.  As a matter of fact the Stoic had only scorn for naturalism.  Physical man was to him a creature to be chained.  Trust not the “scelerata pulpa; peccat et haec, peccat!” cries Persius in terror.

The earlier naive animism of Greece and Rome had contained more of aesthetic value, for it was the very spring from which had flowed all the wealth of ancient myths.  But the nymphs of that stream were dead, slain by philosophical questioning.  The new poetic myth-making that still showed the influence of an old habit of mind was apt to be rather self-conscious and diffident, ending in something resembling the pathetic fallacy.

Epicureanism on the other hand by employing the theory of evolution was able to unite man and nature once more.  And since man is so self-centered that his imagination refuses to extend sympathetic treatment to nature unless he can feel a vital bond of fellowship with it, the poetry of romance became possible only upon the discovery of that unity.  This is doubtless why Lucretius, first of all the Romans, could in his prooemium bring back to nature that sensuousness which through the songs of the troubadours has become the central theme of romantic poetry even to our day.

Nam simulac species patefactast verna diei ... 
Aeriae primum volucres te diva tuumque
Significant initum perculsae corda tua vi,
Inde ferae pecudes persultant pabula laeta.

Vergil, convinced by the same philosophy, expresses himself similarly: 

Et genus aequoreum, pecudes, pictaeque volucres
amor omnibus idem.

And again: 

Avia tum resonant avibus virgulta canoris
Et Venerem certis repetunt armenta diebus
Parturit almus ager Zepherique trementibus auris
Laxant arva sinus.

It is, of course, the theme of “Sumer is icumen in.”  Lucretius feels so strongly the unity of naturally evolved creation that he never hesitates to compare men of various temperaments with animals of sundry natures—­the fiery lion, the cool-tempered ox—­and explain the differences in both by the same preponderance of some peculiar kind of “soul-atoms.”