Diya is a symbol of light, which defines positivity and celebration. There are a lot of ways of looking at it but here is the most interesting metaphor we came across, "The oil in the diya symbolises the dirt in the human mind-such as greed, jealousy, hatred, etc - which human beings tend to nurture. The diya presents light when the oil is burnt by the wick. Hence, lighting of the diya signifies that one needs to get rid of the selfish and materialistic thoughts in order to nurture pure thoughts."