If people are purely selfish, then everything is lost anyway - selfishness is not able to sustain a human society. And while people have to be selfish to some degree to sustain their lives, I see no reasons why they can not act altruistically after they secured basic human needs like food and shelter.
And I agree that most if not all decisions are based or should be based on the expected gain, but the question is then of course how you define or measure that gain. There may actually be a real gain for a country if you spy on other countries, but I argue that this is the wrong standard for gain in that situation, a selfish definition of gain. I would strongly prefer to consider the gain or loss for the whole world when evaluating decisions like whether or not to spy on other countries.
And I agree that most if not all decisions are based or should be based on the expected gain, but the question is then of course how you define or measure that gain. There may actually be a real gain for a country if you spy on other countries, but I argue that this is the wrong standard for gain in that situation, a selfish definition of gain. I would strongly prefer to consider the gain or loss for the whole world when evaluating decisions like whether or not to spy on other countries.