That we're in the middle of an exponentially growing creation of new knowledge, and that (echoing Deutsch) all problems are soluble. Now, there are exceptions to this, for example, a sudden existential crisis. But I prefer to be an optimist in those scenarios, given humanity's demonstrated ability to achieve great things. There's a lot of negativity in the press about the global response to COVID-19, but I take a contrarian view and expect historians to look back at the heroic deeds of healthcare workers and researchers to overcome this crisis as unprecedented in scale and speed. It has exposed cracks in our institutions, surely, but I see it has a crystalizing moment to remind us all how much we can achieve.