When asking the second crucial question in regression anlysis, Does the trend continue outside of the data?, we enter into an area where mathematics blends into philosophy and natural science.

For who is to say what the answer to this question is? All we ever know is the data. Everything else is a guess.

And yet, we must formulate some sort of an answer to this question if we wish to interpolate and extrapolate with confidence.

When there is something that we don't know about the world, science teaches us to go out and collect data. Don't guess. Don't speculate. Get the facts! Data is the very foundation of experimental science. But it can't tell us more than it does. Data is like an inscrutable friend, never offering us a clue about its inner workings unless we draw it out.

It is up to us, in our quest for understanding, to look for patterns and speculate on larger trends. When we've collected enough data, and found a simple way to describe it all, we may say that we have discovered a natural law. We may come to believe that the natural law exists independently of our observations. We are aware that further data may break the pattern, forcing us to reassess. We never know for sure. Humans are forever interpolating in their search for greater truths about the world.