How we cite our quotes: (Chapter.Page)
Quote #1
By mistake, Brangain brought the love potion and handed it to Tristan, who drank and passed it to Yseut. Both thought it was good wine: neither knew that it held for them a lifetime of suffering and hardship and that it was to cause their destruction and their death. (1.44-45)
According to this quote, once Tristan and Yseut drink the love potion, their fate is sealed. There seems to be no opportunity for Tristan and Yseut to make a choice to love one another, or at least, to act any differently from the way they eventually do. The love potion symbolizes both powerlessness to resist love and powerlessness to change your fate.
Quote #2
Hear now of the hunch-backed dwarf, Frocin. He was outside looking at the heavens, and he could see Orion and Venus. He knew the courses of the stars and he observed the planets. He knew what was to happen in the future: when he heard that a child was born, he could predict all the events of its life [...] He looked at the conjunction of the stars and his face flushed and swelled with rage, for he learned that the king was menacing him and would not rest until he had killed him. (2.54)
Frocin's ability to predict the future from reading the stars seems to eliminate the possibility of free will, since the events of a child's life are determined from the moment he is born. Yet Frocin's response to the future he reads for himself—flight to Wales—suggests that if you know your own future, you can change it.
Quote #3
'Indeed, sir, you do not know the reason for her love for me. It is because of a love potion that she loves me. I cannot part from her nor she from me. That is the truth.' (7.79)
The removal of choice from Yseut's love for Tristan also means that Tristan does not do anything to deserve it. His understanding of Yseut's reasons (or lack thereof) for loving him is interesting in this context, in which a holy hermit has just asked Tristan to turn to God. That's because in traditional Christian theology, what makes God's love unique is that it, too, is totally unconditional.
Quote #4
'Sir, by Almighty God, he loves me and I love him only because of a draught that I drank and he drank. That was our misfortune. Because of this the king has driven us out.' (7.79)
Like Tristan, Yseut understands their love for one another as the result of a specific fate (misfortune) rather than as a choice. She also implies that she and Tristan could not possibly have acted otherwise than in the way that caused the king to drive them out.
Quote #5
No man can turn aside his fate. The villain was not on his guard against revenge for the harm he had done Tristan. (9.86)
Although the evil baron's choice to expose Tristan and Yseut's affair sets his death in motion, the text characterizes it as his fate. Of course, a few pages later, this baron mysteriously appears again, alive, with no explanation. Hey, in stories, at least, fate is reversible.
Quote #6
'Oh God!' he said, 'what a fate! What I have suffered for the sake of love! [...] Alas, how unhappy I am! I was indeed born in an unlucky hour!' (18.152)
Even though the love potion has worn off at this point, Tristan still regards his love for Yseut as an unlucky circumstance, a fate outside of his control. The idea of love as a fate one is powerless to resist is further emphasized by the way Tristan speaks of love as a cruel master before whom he is a suffering servant.
Quote #7
The story is told of two trees that grew miraculously, one from Tristan's tomb and one from Yseut's; their branches intertwined over the apse. Three times King Mark had the trees cut down and three times they grew again. Some say it was the power of the love potion that did this. (19.164)
If the trees growing above Tristan and Yseut's grave represent them, Mark's repeated attempts to cut them down symbolize his desire to separate them and destroy their love. Just like Tristan and Yseut when they were alive, Mark is unable to end their love. These trees' resistance to separation might symbolize the inevitability of Tristan and Yseut's love.