President Ram Nath Kovind has said that Mahatma Gandhi's philosophy of truth and non-violence is useful for the whole world. He said Gandhiji's ideas are still relevant to deal with differences on the basis of religion, race, and language.<br />'' <br />''<span style="color: #222222;">Mr Kovind was speaking after inaugurating a national seminar on spirituality for human and social development in New Delhi today. Stating that more than 65 per cent the country's population are youth, the President said there is a need to connect them with the thoughts of Mahatma Gandhi. Expressing concern over climate change, he called it the biggest challenge for humanity.</span>