“In order to see this, we must not suffice with the general slogan, “darkening by sin,” but must account for how this darkening works. Has sin resulted in our inability any longer to think logically?…Absolutely not. Whenever you discuss anything with another person, you repeatedly presuppose both for yourself and for your discussion partner the capacity for logical thought…We have not ceased on account of sin to be rational creatures. And when we compare our own existence with that of the animals, we are completely conscious of the superiority that we enjoy as human beings, thanks to our human reason….Therefore, it cannot be denied that the darkening through sin is observable here as well. How utterly weak is the power of logical thinking among many people! How numerous are the mistakes and errors in our reasoning into which we have repeatedly fallen! How often does not sloth creep in and permeate research at its deepest level!…But even though we admit all of this, all of this is still no more than a partial defect, and not a darkening that impedes our seeing. No, the actual darkening of sin lies in something else entirely. Sin’s darkening lies in this, that we lost the gift of grasping the true context, the proper coherence, the systematic integration of all things. Now we view everything only externally, not in its core and essence, each thing individually but not in their mutual connection and in their origin from God…. It does not lie in things outside of us, and therefore could be known and reflected upon only to the extent that our spirit lived in vital relationship with God, and was able to trace this coherence of divine thoughts proceeding from God.” -Abraham Kuyper
BTW NOTE: There is more that could be said on this point, of what it means to be “darkened by sin” like, the component of the will that is enslaved, etc. But this is a good explanation that shows how unbelieving scientists can still do good science in several respects.