We view the world through the lens of inner models. These inner models are based on our impressions (samskaras) and Vasanas (tendencies). The reality what we see gets corrupted due to these impressions. We cannot deal with reality as it is because of this.
When people talk about facts, facts are corrupted by the images in the mind. We super impose our images on the facts.
For example there was a group which went for a picnic. The picnic was wonderful. At the end of the picnic every eligible boy married every eligible girl. That was 100% success success. Everything here is a fact. There were two boys and two girls who went for picnic. But our mind starts imagining things and perceptions set in.
This is true for Scientific knowledge also. Basic discoveries in science start with hypothesis ( speculation). Like theory of big bang. Over a period of time, lot of empirical data is collected to substantiate/contradict the hypothesis. Fact becomes fiction.
This happens in religion also. Spiritual realization is indiscribable. Description of that is the fact. Over a period of time, the Truth becomes myth. So on and so forth. We go on living in illusion created by perception.