Emperical data
Am I privileging empirical data, as being always superior to other forms of data? No. Although, on a personal level, making your own observations may be better than testimony about observations made by others. When testimony is involved we not only have to trust the senses, but also the memory, honesty, and communication skills of another individual. But both observation and testimony constitute data.
Data is data.

Quine, in "Ontological relativity",describes knowledge as a web of interconnecting ideas or datapoints. But the web itself is not grounded to anything. The bigger we can make the web of knowledge, the most sure we can be of its central pieces. But since the web has no absolute anchors, there is no knowable absolute truth.

If we build our own web of knowledge, it is limited in scope. Ideally we want to pool the resources of society to build the biggest web possible. However, if we don't lay some ground rules we'll end up with a bunch of separate webs, that we can not connect. So for the purposes of building this grand societal web of knowledge, we must insist that all the data points we use, are public and/or reproducible. This is scientific data. And the resulting web is all scientific knowledge, tying together a vast array of individual experiments in many different countries, in many different fields, and over many centuries.

So while the data that goes in is not particularly privileged, the results that come out are. Rather than saying "I believe" or "I know" science allows "we believe" or "we know". The "facts" that reside at the center of that vast web are the facts known to the greatest certainty that humanity has been able to achieve.
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