I think an additional limit is data. Particularly for sciences with strong path dependence, such as ecology, cosmology, evolutionary biology and (my field) geosciences, time has simply erased nearly all of the record of previous events. This is both a big problem (it is quite frustrating) and an opportunity, as we progress through both discovering new records of the past, and developing new techniques for analyzing existing records through new or improved proxies, instrumentation, or theory. I think it’s obvious to the practitioners that we will never know the vast majority of what we want to know, but we can learn enough of what we need to know to keep moving foreword.