Saruman for or against Sauron?

[davem]

The expressed opinions by the author regarding the events and circumstances of his or her own stories are what carry weight when compared to the speculations of readers, no matter where or in what form the expressed opinions of the author happen to appear. I'm not refering to themes or interpretations of the stories here, I'm refering to events

The most important thing is the internal logic of the secondary world. Galadriel, Saruman, Gandalf & Elrond had the capacity to wield the Ring - at the right time in the right circumstances. If they had not why would Sauron, who knew the nature of the Ring better than any, expend so much effort in trying to retrieve it?

Gandalf is clear

Other evils there are that may come; for Sauron is himself but a servant or emissary. Yet it is not our part to master all the tides of the world, but to do what is in us for the succour of those years wherein we are set, uprooting the evil in the fields that we know, so that those who live after may have clean earth to till. What weather they shall have is not ours to rule. 'Now Sauron knows all this, and he knows that this precious thing which he lost has been found again; but he does not yet know where it is, or so we hope. And therefore he is now in great doubt. For if we have found this thing, there are some among us with strength enough to wield it. That too he knows. For do I not guess rightly, Aragorn, that you have shown yourself to him in the Stone of Orthanc?'

So, is Gandalf lying here? Gandalf states that Sauron 'knows there are some among us with strength enough to wield it', & he is clearly including Aragorn in that 'some'. Do we believe Tolkien or Gandalf?