"It can hardly be denied that such a demand quite arbitrarily limits the facts which are to be admitted as possible causes of the events which occur in the real world"

This quote by Friedrich August von Hayek is referring to the idea that when we try to describe the events that occur in the real life, we often limit ourselves to just specific realities that we deem to be possible causes. This is an arbitrary limitation, as there might be other aspects that we are not considering. By only taking a look at particular truths, we are not considering the full range of possibilities that could be affecting the events that take place. This quote is a tip to be unbiased and think about all potential causes when trying to describe the events that happen in the real life. We ought to not limit ourselves to only particular truths, as this might result in an insufficient understanding of the events that take place.