From one of his works, this Irish poet's epitaph is "Cast a cold eye on life, on death. Horseman, pass by!"
Yeats mean | 'Cast a cold eye/ On life, on death ... [PAR] https://www.quora.com/Cast-a-cold-eye-On-life-on-death-Horseman-pass-by- ... 
First you need to understand that Yeats wrote his own epitaph.