This thought experiment comes from Roderick Firth. Imagine that you are a special entity that is omniscient, omnipercipient, disinterested, dispassionate, consistent and otherwise normal.
You are omniscient in respect to that you know everything that goes on in the world and the consequences of what goes on in the world. Therefore you know the ultimate consequence of every action.
You are omnipercipient in respect to that you experience everything that happens in the world. Nothing gets past you.
You are disinterested in respect to that you have no biases or personal interests towards specific people, animals, or anything else.
You are dispassionate in respect to that you lack any emotions that may drive you to act irrationally. You are consistent in respect that you value logic and reason, therefore will avoid any views that involve contradicting yourself.
You are otherwise normal in respect to that you still hold normal human values such as compassion and care for the wellbeing of others.
Three questions can be asked from this thought experiment:
1: How would you feel about the wellbeing of animals and people in other countries in contrast to your family and friends from the standpoint of the impartial observer?
2: What actions would you take from the impartial observer’s point of view from how you answered question 1?
3: Would you consider the impartial observer the ideal way to observe the world?
If you would like to know more about this topic, the impartiality entry on the stanford encyclopedia of philosophy is a useful resource: https://plato.stanford.edu/entries/impartiality/