Quotations and Literature Forum

I would like to use this quote by George Santayana...but cannot without a reference to the source text..anyone got any clues

"The wisest mind has something yet to learn"

Any ideas would be gratly appreciated

I've been at this game long enough to learn to be very suspicious of quotes that only show up on the Internet as just that, a quote; supposedly attributed to someone famous but never a reference to a source, or put into some greater context. Until I see a verifiable source, I don't believe Santanya ever wrote this, though he may have expressed it in other words. It sounds like a proverb to me.
http://users.rcn.com/jbbrown.massed/USCP1.htm

Here it is attributed to "anonymous"
http://www.maxpages.com/wisdom4u/Anonymous_Quotes

Bartlett's had no listing of the quote either. If he did say it, I would assume that it came from The Life of Reason, his major work.