This is more of a philosophical point of view. I have no significant knowledge of physics, or science. Problem: Can you travel back in time with the intentions of killing yourself at a younger age? Obviously no since your alive in the future, but... I'm going to give you two solutions. Solutions Line 1. We assume time is a line. This line extends in two directions ad infinitum with no beginning. Now we assume every event in our lives has, and will occur ad infinitum. Now if the man in question were to travel back in time he wouldn't be able to kill himself. It wouldn't be possible because he's alive in the future. So a man that plans to kill himself in the past cannot exist in this universe, but there is a possibility that a man was born and he succeeded and that's why he doesn't exist in our time ad infinitum. It does seem pointless in the line universe for someone to exist and then not exist, but it's still a possibility. This man wouldn't change the past or the future since he never existed, but he did exist because he didn't exist. But a man that already exists cannot kill themselves in the past. Solution to 1. He did exist because he didn't exist. Ray 2. We assume time is a ray. Time had a beginning, and we exist in the future with no further point in time. In essence we have freewill. Imagine the man traveling along this ray at the furthest point in time. The man decides to travel to the past. This man has the option to kill himself, but in reality if he did kill himself he wouldn't exist anymore, so he never killed himself. If he did kill himself, he succeeded in changing the future and the past. Solution to 2. We exist in the future with no further point in time so we can travel back and kill ourselves.