It is a common perception that objectivity is a virtue in the pursuit of knowledge, that we need to know things as they really are, independent of our mental conceptions and interpretations. It is also a common perception that science is the form of knowledge that is the most objective, and that is why scientific knowledge makes the most progress.
Yet the principle of objectivity immediately runs into problems in the most famous scientific theory, Einstein’s theory of relativity. According to relativity theory, there is no objective way to measure objects in space and time — these measures are always relative to observers depending on what velocity the objects and observers are travelling, and observers often end up with different measures for the same object as a result. For example, objects travelling at a very high speed will appear to be shorter in length to outside observers that are parallel to the path of the object, a phenomenon known as length contraction. In addition, time will move more slowly for an observer travelling at high speed than an observer travelling at a low speed. This phenomenon is illustrated in the “twin paradox” — given a pair of twins, if one sets off in a high speed rocket, while the other stays on earth, the twin on the rocket will have aged more slowly than the twin on earth. Finally, the sequence of two spatially-separated events, say Event A and Event B, will differ according to the position and velocity of the observer. Some observers may see Event A occurring before Event B, others may see Event B occurring before Event A, and others will see the two events as simultaneous. There is no objectively true sequence of events.
The theory of relativity does not say that everything is relative. The speed of light, for example, is the same for all observers, whether they are moving at a fast speed toward a beam of light or away from a beam of light. In fact, it was the absolute nature of light speed for all moving observers that led Einstein to conclude that time itself must be different for different observers. In addition, for any two events that are causally-connected, the events must take place in the same sequence for all observers. In other words, if Event A causes Event B, Event A must precede Event B for all observers. So relativity theory sees some phenomena as different for different observers and others as the same for different observers.
Finally, the meaning of relativity in science is not that one person’s opinion is just as valid as anyone else’s. Observers within the same frame of reference (say, multiple observers travelling together in the same vehicle) should agree on measurements of length and time for an outside object even if observers from other reference frames have different results. If observers within the same vehicle don’t agree, then something is wrong — perhaps someone is misperceiving, or misinterpreting, or something else is wrong.
Nevertheless, if one accepts the theory of relativity, and this theory has been accepted by scientists for many decades now, one has to accept the fact that there is no objective measure of objects in space and time — it is entirely observer-dependent. So why do many cling to the notion of objectivity as a principle of knowledge?
Historically, the goal of objectivity was proposed as a way to solve the problem of subjective error. Individual subjects have imperfect perceptions and interpretations. What they see and claim is fallible. The principle of objectivity tries to overcome this problem by proposing that we need to evaluate objects as they are in themselves, in the absence of human mind. The problem with this principle is that we can’t really step outside of our bodies and minds and evaluate an object.
So how do we overcome the problem of subjective error? The solution is not to abandon mind, but to supplement it, by communicating with other minds, checking for individual error by seeing if others are getting different results, engaging in dialogue, and attempting to come to a consensus. Observations and experiments are repeated many times by many different people before conclusions are established. In this view, knowledge advances by using the combined power of thousands and thousands of minds, past and present. It is the only way to ameliorate the problem of an incorrect relationship between subject and object and making that relationship better.
In the end, all knowledge, including scientific knowledge, is essentially and unalterably about the relationship between subjects and objects — you cannot find true knowledge by splitting objects from subjects any more than you can split H2O into its individual atoms of hydrogen and oxygen and expect to find water in the component parts.