Because what you don't know is still real anyway, so if you are not aware of it, it can hurt you. Forewarned is forearmed. Unless you are driving the train, or can contact the driver; Knowing that...
People say ignorance is bliss because the meaning of ignorance is to not have knowledge of something. Imagine a life where you had no knowledge of war, pain, suffering, hatred, etc. It would be bliss...
This phrase is commonly thought to have originated in the 1742 poem titled, "Ode on a Distant Prospect of Eton College" by Thomas Gray. Lines 91-100 To each his sufferings: all are men, Condemned...
The original quote was "If ignorance is bliss, tis folly to be wise." The idea was to illustrate that because we know wisdom is not folly, ignorance should physically pain us. There is a story about...