Modern cosmology says the local curvature of the universe is very small, so there is a 50 % chance of the curvature being positive/negative. This naively suggests a 50 % chance of the universe being infinite, but only if one extrapolates local properties to everywhere. To my mind, that is like seeing a road extending all the horizon, and then claiming the road is infinite. Ok, we can see the universe is homogeneous over much larger distances than the road, but infinite is infinitely larger than those distances, so we have zero evidence about the universe being infinite.
Moreover, as you note:
Modern cosmology says the part of the universe we can causally influence is finite.
Even if the universe is flat (apparently what most cosmologists think, even though the data arguably points towards 50 % of the curvature being positive/negative, and very low chance of it being null), it can still be finite if the universe is a multiply connected space (see shape of the universe). Most cosmologists assume a simply connected space, which together with flatness implies the universe is infinite, but I not think there is evidence supporting one type of connectivity over the other. “The issue of simple versus multiple connectivity has not yet been decided based on astronomical observation”.
In addition, from the point of view of the cost-effectiveness of our actions, what matters is not only the scale of the consequences of our actions, but also their neglectedness. Scale is directly proportional to the number of lives, but neglectedness is inversely proportional to the number of lives. Consequently, the size of the universe (how many lives it will have) alone does not affect the cost-effectiveness of our actions. Longtermism can work if we have reasons to think people alive today have an unusual influence over the whole universe, i.e. if the hinge of history hypothesis is true. However, if the universe one could causally affect was infinite, there would be infinite people in the hinge of history, which means our time would no longer be hingy. In other words, the effect of having a larger scale in an infinite universe would be cancelled out by that of having a lower neglectedness.
In my view, “the dream” of causal expected total hedonistic utilitarianism is very much internally consistent, and alive. In principle! In practice, one has to rely on heuristics like decreasing the number of nuclear weapons.
Hi Joe,
Modern cosmology says the local curvature of the universe is very small, so there is a 50 % chance of the curvature being positive/negative. This naively suggests a 50 % chance of the universe being infinite, but only if one extrapolates local properties to everywhere. To my mind, that is like seeing a road extending all the horizon, and then claiming the road is infinite. Ok, we can see the universe is homogeneous over much larger distances than the road, but infinite is infinitely larger than those distances, so we have zero evidence about the universe being infinite.
Moreover, as you note:
Modern cosmology says the part of the universe we can causally influence is finite.
Even if the universe is flat (apparently what most cosmologists think, even though the data arguably points towards 50 % of the curvature being positive/negative, and very low chance of it being null), it can still be finite if the universe is a multiply connected space (see shape of the universe). Most cosmologists assume a simply connected space, which together with flatness implies the universe is infinite, but I not think there is evidence supporting one type of connectivity over the other. “The issue of simple versus multiple connectivity has not yet been decided based on astronomical observation”.
In addition, from the point of view of the cost-effectiveness of our actions, what matters is not only the scale of the consequences of our actions, but also their neglectedness. Scale is directly proportional to the number of lives, but neglectedness is inversely proportional to the number of lives. Consequently, the size of the universe (how many lives it will have) alone does not affect the cost-effectiveness of our actions. Longtermism can work if we have reasons to think people alive today have an unusual influence over the whole universe, i.e. if the hinge of history hypothesis is true. However, if the universe one could causally affect was infinite, there would be infinite people in the hinge of history, which means our time would no longer be hingy. In other words, the effect of having a larger scale in an infinite universe would be cancelled out by that of having a lower neglectedness.
In my view, “the dream” of causal expected total hedonistic utilitarianism is very much internally consistent, and alive. In principle! In practice, one has to rely on heuristics like decreasing the number of nuclear weapons.