While it is true that science cannot decide questions of value, that is because they cannot be intellectually decided at all, and lie outside the rea… - Bertrand Russell

Not to be absolutely certain is, I think, one of the essential things in rationality.

When I was a child the atmosphere in the house was one of puritan piety and austerity. There were family prayers at eight o'clock every morning. Although there were eight servants, food was always of Spartan simplicity, and even what there was, if it was at all nice, was considered too good for children. For instance, if there was apple tart and rice pudding, I was only allowed the rice pudding. Cold baths all the year round were insisted upon, and I had to practice the piano from seven-thirty to eight every morning although the fires were not yet lit. My grandmother never allowed herself to sit in an armchair until the evening. Alcohol and tobacco were viewed with disfavor although stern convention compelled them to serve a little wine to guests. Only virtue was prized, virtue at the expense of intellect, health, happiness, and every mundane good.

The essence of the Liberal outlook lies not in what opinions are held, but in how they are held: instead of being held dogmatically, they are held tentatively, and with a consciousness that new evidence may at any moment lead to their abandonment.