Quote Originally Posted by weekilter
Just read a post on another forum who claimed that the name Stewart was not Scottish and that only the name Stuart was Scottish. I'm wondering if this is the same type argument one might make between surnames that start with Mac versus names that start with Mc.
"Mac" and "Mc" are the same thing -- "Mc" is just an abbreviation of "Mac". Sometimes you'll even see "M'Donald", "M'kenzie", etc.

The Clan Stewart Society (US) has this to say about the spelling variants on their FAQ page:

What is the significance of the different spellings (Stewart, Stuart, Steward, etc.)?
The original spelling of the name was derived from Gaelic words for the keeper of the household and certain included accounts (steward) and the royal hereditary position, High Stewart of Scotland, created by King David I. From its beginning as a name, it was spelled with a "t" instead of a "d" on the end. The Stuart spelling resulted from the movement of Scots back and forth to France. At the time there was no "w" in the French language so the Stuart spelling is a French version, brought back to Scotland from France. Other spellings have resulted from the names being changed because they were recorded as some one heard them or because the correct spelling was simply not known.
The following are the known variations of the surname "Stewart": Sdiuord, Steuard, Steuarde, Steuart, Stevarde, Stevarte, Steward, Stewart, Stewerd, Stigeweard, Stiuard, Stiubhard, Stiubhart, Stiward, Stuard, Stuarde, Stuart, Stuarte, Stuerd, Stuward, Styward, Stywarde, Steart, Stueart and in Italy & Spain – Estuardo

-- http://www.clansstewart.org/faq.html
I would tend to go with these folks rather than the "absolute" statement that this fellow has made.

Cheers,

Todd