LotR -- Book 3 - Chapter 01 - The Departure of Boromir

[Encaitare]

Whatever point Tolkien is making with these attributions - the Eye to Sauron, the Voice to Gandalf & the Hand to Saruman - escapes me at the moment, but it is certainly intriguing.

The Voice and Gandalf seem the clearest to me -- Gandalf is a persuader. He urges people to take action, to take the proper course, since he himself cannot do certain things for them. He cannot challenge Sauron openly, and so he must use others to achieve the necessary ends. For example, he gives counsel to Denethor, Theoden, and all those at the Council of Elrond.

Saruman, on the other hand, (no pun intended) is different. He takes things into his own hands -- or Hand -- and sets about doing things his own way. He fancies that he might obtain the Ring, an instrument or weapon worn on the Hand.

It's interesting that Saruman is not attributed with the Voice in this sense, since his voice is his greatest source of power and influence. It's as though Gandalf is the voice of reason, and Saruman is that of lies -- he will make promises and false claims, but in the end it will all just come to better serve himself.

As for the Eye, Sauron is able to see many things, both through "tracking" the Ring, and through the use of the Nazgul and his spies. That's all I can really think of for him right now.