"Those who promise us paradise on earth never produced anything but a hell"

This quote by Karl Popper is a warning versus utopianism, or the belief that a best society can be created in the world. Popper is recommending that those who assure a paradise in the world are misguided, as they are not able to provide on their guarantees. Rather of producing a paradise, they are more likely to produce a hell. This is because utopianism is an impractical and optimistic goal that is difficult to achieve. Popper is alerting us that utopianism is a dangerous and misdirected belief, and that it is better to concentrate on achievable goals that can improve society, rather than attempting to produce an ideal world. He is suggesting that we ought to be realistic and practical in our approach to producing a much better society, instead of trying to attain an unattainable paradise.