Flip Flopping

When a public figure changes his mind, you often here commentators point this out as a weakness.

Here is how Einstein looks at this issue (from Walter Isaacson's Einstein biography):

Like a good scientist, Einstein could change his attitudes when confronted with new evidence. One of his deepest personal principles was pacifism. But in 1933, with Hitler's ascension, the facts had changed. 

The charge of inconsistency amused Einstein. For a scientist, altering your doctrines when the facts change is not a sign of weakness.