¹Technische Universität Kaiserslautern, Kaiserslautern, Germany

One of the famous phrases by Immanuel Kant (1724–1804) is: 'Thoughts without content are empty, intuitions without concepts are blind' (Kant 1781, p. A 51, B 75; in the original German: 'Gedanken ohne Inhalt sind leer, Anschauungen ohne Begriffe sind blind').

This sentence was frequently replaced by other authors during the epoch of Kant's criticism by Sensations are blind without concepts,
concepts empty without sensations (original: 'Anschauungen ohne Begriffe sind blind, Begriffe ohne Anschauungen leer.').

'Sensations' are perceptions by the senses or 'awareness ... by means of the nervous system' (Chambers Pocket Dictionary), while a 'concept' is meant as a term or designation or 'a notion, an abstract or general idea' (Chambers Pocket Dictionary).

Sensations and concepts correspond with one another – in both directions. As soon as we sense anything, we complete it by a concept – if available. As soon as we hear or read a term (i.e. a concept), we try to supplement it by a sensational image (Boulding, 1956).

Based upon sensations we all build pictures or images at our 'internal stages' – and add concepts: If we see a bird, for example, a sparrow, we immediately add the concept or term 'bird' or 'sparrow'. If – on the other hand – we hear somebody talk about a bird or a sparrow, we immediately add the image of a bird or a sparrow in our brain. In both cases, there is mutual interaction between the concept and the sensation.

It can also be that we sense an airplane or a helicopter or a kite that flies above our heads, and we can immediately recognise it as an airplane, a helicopter, or a kite, respectively; that is, we conceptualise. Only if any kind of UFO is flying above our heads, it is an 'unidentified flying object', a case of 'blind' sensation, that is, a sensation without a (realistic) concept.

If – on the other hand – we hear or read some news about a 'nignag' (not a knickknack!), we have no sensual equivalent at our internal stage. The nignag is an 'empty' concept, that is, a concept without sensation. We do not understand the sentences about the nignag unless it is described in such a way that we can build an image of a nignag.

It was 200 years after Kant's Critique of Pure Reason that medical doctors discovered that the two hemispheres of the brain function in quite different ways.

They found that the left hemisphere (of a right-handed person) deals with logic, language, mathematics, etc. while the right hemisphere deals with holistic impressions, pictures, images, and (less structured) wholes. Both hemispheres are connected by the 'corpus callosum' bridging the fissure between the two hemispheres. Mutual compensation seems to occur through the 'corpus callosum': sensations are mirrored and supplemented by concepts, while concepts are mirrored and supplemented by sensational images.

As a consequence of this crossing of nervous tracts, the left hemisphere of the brain is connected with the right eye – and vice versa.

If the right hemisphere 'sees' (through the left eye) a square, the left hemisphere will add the concept 'square', 'four 90° angles', 'four sides of equal length', etc. Or the left hemisphere might remember the name 'Hyde Park', and the right hemisphere will add images of the Hyde Park, etc. The right hemisphere might recall paintings of French impressionist artists, and the left hemisphere will add the names, such as Degas, Cézanne, Manet, Monet, Pissaro, Renoir, Seurat, Signac, Sisley.

The discovery of the different functions of the two hemispheres of the brain includes that one hemisphere tends to dominate the other one, either the left dominates the right one or the right the left one. This discovery led to the frequently quoted paper 'Planning on the left side and managing on the right' by Henry Mintzberg (1976). The analysts, planners, researchers, etc. tend to be dominated by the left hemisphere, the leaders, decision makers, and managers by the right hemisphere.

Isn't it surprising that Kant and his school of criticism anticipated the research results of brain surgery and brain-psychological research, some 200 years ahead: the separation of sensations (the domain of the right hemisphere of the brain) from concepts (the domain of the left hemisphere of the brain)? Sensations provide holistic impressions and entire images, while concepts depend on language, logic, and mathematics. The 'corpus callosum' is busy to find the concepts corresponding with the sensations as well as the sensual images corresponding with the concepts.

It seems as if Kant's sensations-concepts correspondence has not as yet been related to the division of labour between the right and the left hemisphere of the brain.

The distinction between sensations and concepts has consequences for knowledge management:

1. In many cases, concepts (i.e. terms or designations) tend to be easier to be made explicit while sensations or sensual images may tend to remain tacit.
2. Software for the support of knowledge management should include some of the functions of the 'corpus callosum' in that they help to find corresponding sensations for concepts as well as concepts for sensations.