There are so many interesting relationship dynamics between the characters in the Lord of the Rings, and one of the most fractious is that of Denethor, the Steward of Gondor, and Gandalf the white wizard. There is definitely a strain between them because Gandalf has a strong bond with Aragorn, who is the rightful king of the throne that Denethor sits upon.
It is necessary for Aragorn to become king, in order to reunite the people of Middle Earth and help win the war against Sauron, but all Denethor sees is a traitorous wizard who is trying to steal his rule. So if the steward is so distrusting of the wizard, then why does he allow Gandalf into the ancient archives of Gondor, whilst Gandalf searches for Isildur’s original encounter of the one ring? Many believe it is because, at this point, Denethor had not yet succumbed to his paranoia, and was not so distrusting of the wizard yet.
There is much debate about the 17 years that pass between Bilbo’s 111th birthday party, and Frodo leaving the Shire, especially among book fans vs Peter Jackson movie lovers. In the books, it is known that during this time, Gandalf is greatly troubled by the changes he has seen in Bilbo, and concerned about the unusual ring that Bilbo carries always on his person. He, therefore, sets out, alongside Aragorn, to try to capture Gollum and hear his account of the evil object.
After years of pursuing Gollum, Aragorn does eventually capture him before meeting the hobbits at the Prancing Pony, but during this time, Gandalf has decided instead to go to the old halls of Gondor, and see what he can learn in the scrolls there of Isildur’s downfall, and the gaining and losing of the ring of power. As the last confirmed place of the ring was the site of Isildur’s death, where it fell into the river Anduin, starting with the old king’s account seems like the best clue, but during the recent years of Gandalf’s quest, Denethor has become less and less friendly towards the wizard and his so-called scheming.
During the council of Elrond in Rivendell, Gandalf recounts his journey to the others, telling them “‘With that thought, I forsook the chase, and passed swiftly to Gondor. In former days the members of my order had been well received there, but Saruman most of all. Often he had been for long the guest of the Lords of the City. Less welcome did the Lord Denethor show me then than of old, and grudgingly he permitted me to search among his hoarded scrolls and books.”
Many consider it surprising that Denethor let Gandalf in at all, considering at this point he may already be looking into the Palantir, and learning all about the re-arrival of Aragorn. There is a possibility that Denethor lets Gandalf in to read the scrolls because he believes he will find nothing in there, just as Saruman has done, despite perusing the ancient texts for many years. But it is far more likely that Denethor let Gandalf in because, deep down, he knows that the fate of the world is at stake.
Despite the Peter Jackson portrayal suggesting that Denethor refuses all help from the wizard, in the books, Denethor cares above all else, about the kingdom of Gondor, and Boromir’s chance to rule it. That is why he sends Boromir to retrieve the ring in the first place, because he genuinely believes it is what is best for his failing people. And although already at this point Denethor is aware of Aragorn and his possible cohorts with Gandalf, the Steward is not yet so distrusting and so far gone that he wouldn’t put the health and protection of his people above his own petty fears and jealousies. He already has pieces of the truth, and a subtle feeling growing, that a darkness unlike any before is coming, so if Gandalf can indeed find anything in the library that would stop Sauron’s terrible return, it would be to the benefit of all.
It is only after the War of the Rings hits full force when Frodo and Sam begin journeying towards Mount Doom, news of Saruman’s betrayal reaches Gondor, Boromir dies along the road with the fellowship, and all of Mordor’s orcs begin marching upon his lands, that Denethor begins to truly succumb to his anger and paranoia. At this point, he gives up on all hope and begins to despair to the point of believing that the only way for Gondor to avoid the terrible fate of the rest of Middle Earth is for them all to die. This is why he tries to sacrifice himself and his son Faramir on the pyre, and this is why he is beyond even Gandalf’s help.