Free will is a theme in Tenet. There are suggestions that Tenet 's universe is deterministic, so what happens (including bootstrap paradoxes) will always happen, and consequently, there is arguably no free will. One of the film's common refrains, "ignorance is our ammunition", could hint at the illusionist stance that free will does not exist but people should act as if they have free will. However, the characters (especially Neil) express uncertainty as to whether history can be altered, and say several times during the film, "what's happened, happened". Neil's attitude towards free will could be interpreted as compatibilist, whereby free will and determinism are seen as compatible. Kat is seen as the character who most strongly embodies free will in Tenet by choosing to stray from the plan and shoot Sator, at which point she is free from his control. Kat relays to the Protagonist that when she was returning with Max to Sator's yacht in Vietnam and saw a woman (her future self, unbeknownst to past Kat) diving gracefully off the yacht, she felt jealous of that woman's freedom. Similarly, there is uncertainty in Tenet regarding the grandfather paradox and whether the use of the Algorithm in the future, wiping out the past (the time of the events in Tenet), would also wipe out the future. Tenet has been interpreted as a war between past and future.