Image of man — the ‘scientific’ versus ‘manifest’ images of Wilfrid Sellars

We are exhorted to make our medicine rigorously evidence based and yet robustly patient centred. We find ourselves having to square a circle. Why is it that these two aspects of medicine seem so determined to pull apart? And why is it that the scientific picture of evidence-based medicine always gets to play front of stage?

The US Philosopher Wilfrid Sellars describes two images or pictures of man. The scientific image of man is familiar to medics; it’s all about body tissues, genes, and biochemistry. But what if science is not the only valid way of knowing? Sellars sees the ‘manifest image’ of man as ‘the framework in terms of which, to use an existentialist turn of phrase, man first encountered himself’. The manifest image is connected to personhood and self-awareness, it is how I think of myself every day. Pascal said, ‘Man is but a reed, the most feeble thing in nature; but he is a thinking reed … But, if the universe were to crush him, man would still be more noble than that which killed him, because he knows that he dies and the advantage which the universe has over him; the universe knows nothing of this’. Consciousness, although contingent and frail, is qualitatively unique and is of great value.

Scientific knowledge is not the only sort of knowledge that is important to persons. ‘I love my wife’ is an important piece of knowledge to me, but it cannot be derived scientifically. It is an example of what is sometimes called ‘personalistic knowledge’.

Frank Jackson formally demonstrates the validity of such personalistic knowledge. If physical science can tell us all that can be known then a colourblind person must be able to know what it is to see red. We can construct this knowledge scientifically around a model of having the right sort of cones in the retina to perceive incident light with a wavelength of 650 nm. Yet if this person, in possession of all available knowledge about redness, were to be cured of their colour blindness then they will learn something new that they did not know before, what it is to see red. Jackson’s argument is a demonstration of something both profound and also obvious to all but the most extreme physicalist. What it is to be me cannot be contained within a scientific account of the self.

Sure, we could join a narrow band of neuroscientists and say that our consciousness is a cognitive delusion. The belief that the methods of natural science are valid in all fields of human enquiry is called ‘Scientism’. Scientism seems touchingly modernistic, and reminiscent of other imperialist systems such as Communism, or Hegel’s belief that in fact it is philosophy that defines and encompasses all truth.

Sellars claims that the scientific image of man is not able to encompass or comprehend the manifest image but that both are equally valid ways of knowing about man. As humans, personalistic knowledge is our fundamental concern. If science showed that in fact E = MC³ I would be surprised but not fundamentally disturbed. But mess with my personalistic knowledge and that affects me deeply.

• © British Journal of General Practice 2013