THE BELFAST ADDRESS. 451 
Lucretius, which forms the basis of Mr. Tennyson's noble 
poem, is in strict accordance with his philosophy, which 
was severe and pure. 

SECTION 2. Still earlier than these three philosophers, 
and during the centuries between tiie first of them and 
the last, the human intellect was active in other fields than 
theirs. Pythagoras had founded a school of mathematics, 
and made his experiments on the harmonic intervals. The 
Sophists had run through their 'career. At Athens had 
appeared Socrates, Plato, and Aristotle, who ruined the . 
Sophists, and whose yoke remains to some extent unbroken 
to the present hour. Within this period also the school 
of Alexandria was founded, Euclid wrote his "Elements" 
and made some advance in optics. Archimedes had pro- 
pounded the theory of the lever, and the principles of 
hydrostatics. Astronomy was immensely enriched by the 
discoveries of Hipparchus, who was followed by the his- 
torically more celebrated Ptolemy. Anatomy had been 
made the basis of scientific medicine; and it is said by 
Draper* that vivisection had begun. In fact, the science 
of ancient Greece had already cleared the world of the 
fantastic images of divinities operating capriciously 
through natural phenomena. It had shaken itself free 
from that fruitless scrutiny " by the internal light of 
the mind alone," which had vainly sought to transcend 
experience, and to reach a knowledge of ultimate causes. 
Instead of accidental observation, it had introduced obser- 
vation with a purpose; instruments were employed to 
aid the senses; and scientific method was rendered in a 
great measure complete by che union of Induction and 
Experiment. 
What, then, stopped its victorious advance? Why was 
the scientific intellect compelled, like an exhausted soil, to 
lie fallow for nearly two millenniums, before it could 
regather the elements necessary to its fertility and strength? 
Bacon has already let us know one cause; Whewell ascribes 
this stationary period to four causes obscurity of thought, 
servility, intolerance of disposition, enthusiasm of temper; 
and he gives striking examples of each, f But these char- 
*-" History of the Intellectual Development of Europe," p. 295. 
\ " History of the Indu,cti,ve Sciences," vol. i. 
