Four sitting presidents have been killed, all of them by gunshot: Abraham Lincoln (the 16th President), James A. Garfield (the 20th President), William McKinley (the 25th President) and John F. Kennedy (the 35th President).
Answer:
On 28 May 1588, the Armada set sail from Lisbon and headed for the English Channel. The fleet was composed of 130 ships, 8,000 sailors and 18,000 soldiers, and bore 1,500 brass guns and 1,000 iron guns.
Philosophy would be the answer :)