Did Gandalf make a mistake at Isengard ?

[PrinceOfTheHalflings]

Originally Posted by Formendacil

Although the basic point here that Inziladun and {b]Ibrin[/b] are making is to the effect that the palantír did not play a deliberative role in Gandalf's actions, I think it's incorrect to say that he did not know a palantír was in Saruman's possession.

The Orthanc-stone, after all, had always been at Isengard.

Gandalf probably did not know of the Orthanc-stone. Even Saruman did not know for certain that the Orthanc-stone was there until he moved into Isengard:

"Saruman had no doubt from his investigations gained a special knowledge of the Stones, things that would attract his attention, and had become convinced that the Orthanc-stone was still intact in its tower. He acquired the keys of Orthanc, nominally as warden of the tower and lieutenant of the Stewards of Gondor. At that time the matter of the Orthanc-stone would hardly concern the White Council. Only Saruman, having gained the favour of the Stewards, had yet made sufficient study of the records of Gondor to perceive the interest of the palantíri and the possible uses of those that survived; but of this he said nothing to his colleagues." (from Unfinished Tales)

So, in Tolkien's own words, only Saruman had much interest in, or knowledge of, the Stones and he never mentioned them to other members of the White Council. In other words: Gandalf probably did not know about the Orthanc-stone.