What is Knowledge?

I agree with you that knowledge is subjective but there should way to validate it from evidences. A hypothesis is originally developed through a psychological representation of the state of an object. Statistical thinking was originally developed to construct an image for the handling of an object with extremely complex structure. Image of the distribution of molecular velocities adopted by Maxwell is obviously a conceptual image. Boltzmann further developed the use of the distribution for the handling of entropy and this finally led to the introduction of the concept of quantum by Max Plank. These are well-known historical events in physics. The justification of the use of such an image is provided through the confirmation of the predicted results. These examples clearly demonstrate the subjective nature of the image developed for the handling of scientific problems.
Although the model is originally defined subjectively it becomes useful for others through the accumulation of successful examples of its predictive use. Eventually this provides an objectivity.
For detail (how we can proceed toward objectivity) you can see paper by Hirotugu Akaike, "Making statistical thinking more productive" Annals of the Institute of Statistical Mathematics. ISSN: 0020-3157 (Print) 1572-9052 (Online).
We will try to discuss how statistics can be well conceptualized as a new branch of epistemology and can help us to proceed towards objectivity from subjectivity (see slogan of statistics group) at platform of statistics group