The Reason is a Document in Rise of the Tomb Raider. It belongs to the Journal of Lord Croft set and contains Lara's father's research note and other, more personal messages to Lara. They mainly cover his problems with his research after his work was discredited as a fools errand.
I face constant ridicule from people I once considered colleagues and friends. They have no idea.
There is a truth behind all myth. The stories of all cultures speak a universal language and they point to a startling possibility: the world is not what we think. Our lives are not what we think.
If I continue, I face isolation. I will become a pariah.But... I will continue. For Amelia. It was her death that set me on this path. And for her, I cannot waver. I wish every night that she was still here. That I'd had the tools to help her.