未知生，焉知死。

Confucius 论语 先进第十一

Wèizhī shēng, yān zhī sǐ.
未知生，焉知死。
While one does not understand life, how can he understand death. 

未 not, not yet; 
知 know, understand; 
生 life, living; 
焉 how, why; 
死 dead, pass out.