In his maiden speech, Mr Hague said humans themselves were responsible for the world and how people lived within it.
"I absolutely reject the idea that ethical or moral behaviour has its source in religious faith. On the contrary, my personal philosophy presupposes that there is no higher power that has, for some reason, disadvantaged some people and conversely privileged others or that will intervene to rectify this disparity or compensate its victims. In the absence of such external power then the responsibility for determining how we should live together and for acting to achieve that state is solely, but collectively, ours."
He also laid out his personal philosophy - a vegetarian for the past 28 years, Mr Hague said he become so "to take only what resources I need from the natural world and to harm the natural world to the least extent possible".
He felt a "growing unease" that the human race had reached the limits of what it could take from the natural world.
"Human beings are not well adapted to deal with gradually unfolding risk or dangers that are rare but catastrophic."
He said technological advances had saved humankind from the worst consequences of their actions in the past, but he feared it would not be enough this time. He looked to the United States for some hope for the future, describing Barack Obama's election as kindling "a small flame of hope for the future of the human race and the planet".
Mr Hague has long been an activist for human rights and is a well-known advocate for the gay community.
In the 1980s he was active in anti-apartheid campaigns in the mid-1980s - including the 1985 campaign to stop the tour of the All Blacks to South Africa.
He spoke of the power one individual could have, recalling standing in his grandparents' house 40 years ago, "tears streaming down my mother's face" while listening to the radio announce the assassination of Robert Kennedy.
He quoted "Bobby" Kennedy's address to the National Union of South African Students in 1966.
In that, the former US senator said just one man speaking out could "send forth a tiny ripple of hope ... those ripples build a current that can sweep down the mightiest walls of oppression and resistance".
Mr Hague said while he was certain his part would not be as significant as that of Kennedy or Obama, "I commit to do my best."
"Let us now cast our pebbles into the pond."
Mr Hague was chief executive of the West Coast District Health Board, before which he was executive director of the Aids Foundation.
He has a love of the outdoors as a keen mountain biker and cycling advocate, and is pushing for a national network of off-road cycling tracks. His list of career involvements has given him a broad constituency - he lists cyclists, outdoor lovers, public health workers and gay, lesbian and the "wider rainbow family" among those he aims to represent. He has a partner, Ian, and a son, Thomas.
Mr Hague is on the health select committee and is Green Party spokesman on health and wellbeing, commerce, small business, tourism, biosecurity & customs, cycling & active transport, sport & recreation, rainbow Issues and rural affairs.