A pas de trois is a dance for how many people?

Which philosopher, author of "A Treatise of Human Nature", was born in Edinburgh in 1711? What is the partial or total loss of memory called? What do you call a being in mythology who is partly divine and partly human? "A partridge in a pear tree" is a gift in which Christmas carol? What is a vertical passage sunk into the ground for mining called? A patent for the first successfully manufactured electric razor was issued to which man in November 1928? A patient who told a Frankfurt doctor "I have lost myself" was the basis for his 1906 lecture. Who was the doctor? What is a paved outdoor area next to a house called?