Before Kuhn wrote The Structure of Scientific Revolutions, scientists believed that their disciplines progressed logically. Knowledge might stagnate for centuries, as it did in the Middle Ages, but it could not easily regress, and each advance rested on all that had gone before. A faith in this inexorable, logical progress of scientific knowledge remained long after a similar faith in moral progress had been discredited. Indeed, it is possible to find in the writings of Karl Popper, for example, a belief that scientific knowledge was the truest, or purest kind we could have; and much of this prestige derived from the idea that it provided an escape from the fuzziness of human knowledge towards something sharp- edged and reliable.
Kuhn blew that up. He showed that gigantic scientific advances, such as Newtonian physics, or the heliocentric system, do not improve the theories that precede them in a tidy and logical way. They shoulder them aside completely, so that the old problems are not so much solved as replaced by new, productive ones. This does not mean that scientific statements are arbitrary or untrue. But it does show that they are constrained by scientists' imagination, and this, in turn, is constrained by all the assumptions of the culture in which they work. When some great leap of the imagination surmounts these difficulties, it is almost impossible for others who have grown up in the old way of thinking to follow it. Only the young can fully take advantage of the new discoveries. His term for these giant changes, since grossly abused, was a "paradigm shift".
However, it is fair to describe his own work as a paradigm shift, and the effects of this have been working their way through all sorts of disciplines ever since. His work was extended, often in directions which he would have disliked, by philosophers of science such as Paul Feyerabend; but always with the same tendency - to diminish the authority of science as a way of reaching out to non-human forms of wisdom. Even scientists, he showed, were confined within the assumptions of their time. Science could no more be the arbiter of all other knowledge than theology could maintain its position as Queen of the Sciences.
This might seem good news for theology. Theology has been steadily displaced as a source of reliable knowledge about the world since the Middle Ages; and science had been doing much of this displacement. If science turns out to be as socially constrained as poetry, then perhaps we should be looking elsewhere for objective knowledge. You will still find a lot of Christians who argue like this, with varying degrees of subtlety: from those who tell you that "evolution is just a theory" to the Pope, for whom the social conditions of first-century Palestine display the objective truth about human nature and the relations between men and women.
The belief that there must be some knowledge that is not socially conditioned is very deeply implanted in us; and there are many very good reasons for wanting to reject the idea that science or anything else cannot connect with objective truth. This century has probably seen more deliberate lying than any other in history. Against this, the idea that "you shall know the truth, and the truth shall set you free" is hard to give up. It is probably wrong to give up, too, because "socially constructed" does not mean "unconstrained". Money is socially constructed: that does not mean it does what we want.
Science is socially constructed: but it must still explain the tendency of dropped objects to fall and predict the rate at which they will fall. Theology, too, is socially constructed. It carries with it not merely the thoughts of the theologians who have gone before, but a whole burden of assumptions about the way the world works, whether these are to do with the likelihood of miracles or the degree to which patriarchy or slavery are part of the natural order. Within theology there have been paradigm shifts, just as within science. Yet none of these can claim a privileged position.
It is no use appealing to an objective morality, because - even if it exists - we can only approach it through a shared subjectivity, and it is beyond the power of science, beyond even the power of an Archbishop, to be able to give us that back.