The writer expresses his great gratitude to Stephen Hawking. What is the gratitude for?

The writer expressed his gratitude to Stephen Hawking because he had been an inspiration for him. He saw him as the embodiment of his bravest self. He felt that if he had been as brave as Stephen, he would have achieved a lot. He felt he was moving towards that embodiment that he had believed in for many years. That is why he expressed his greatest gratitude to him as he had made him realise what great heights he could reach.