An Australian moral philosopher has delivered the annual Sir Malcolm Knox Memorial Lecture at St Andrews University.

Peter Singer explored the concept of ethical giving in the 21st century during the sold-out talk.

He discussed charity, why we should give, and the importance of giving with our heads not our hearts.

Based on his latest book, Ethics in the Real World, he argues: "Those who have enough to spend on luxuries, yet fail to share even a tiny fraction of their income with the poor, must bear some responsibility for the deaths they could have prevented."

Students were able to engage with the man named by Time magazine as one of the 100 most influential people in the world.

Those in attendance were also urged to think about how to do good; and to debate the strengths and limits of the concept of altruism.