Consciousness is a kind of private "inner world" in which we experience our thoughts, feelings and perceptions. 'But the term can have multiple meanings, which sometimes seem contradictory,' Francken explains. 'Someone is conscious when they respond adequately to outside stimuli. But also when they are daydreaming and not reacting at all. It is important to allow these different meanings to coexist in theories of consciousness.'

Why is consciousness such an interesting subject?

'The subject appeals very much to the imagination. It is often assumed that consciousness enables our unique human capacities, such as reflecting on our behaviour or enjoying music. Moreover, consciousness is what makes life worth living - without consciousness there is literally nothing to it. At the same time, for many people it is something that cannot "just be explained scientifically".'

How is it that we become aware of certain sounds, thoughts or sensations?

'You can think of that question in two ways. The question can be: how can it be that consciousness arises at all from complicated biochemical processes? That is the philosophical question. But the question can also be: how can it be that we are aware of some impressions and not others? One would think that these questions can be answered independently of each other. Many scientists and philosophers see it that way. Instead, we try to show in our book that answers to both questions directly affect each other. We discovered that two completely different approaches or methods are used in philosophy and neuroscience to investigate consciousness. The neuroscientific approach is not "neutral", or "objective", as many scientists think, but contains all kinds of philosophical assumptions.'

If philosophers and neuroscientists were to come up with a definition of consciousness together, what would it be roughly like?

'That definition would have to see consciousness as a kind of cluster concept: a puzzle that requires several pieces to complete the picture. For example, one part is about how it feels to experience something, another part about how we can act on information from different senses, and yet another part about our continuous adaptation to the world around us. Neuroscientists and philosophers are working on the same puzzle, but using pieces that sometimes don't fit together. Although there is still one important starting point that both fields must share in order to work on the same puzzle at all: they both wonder what consciousness does.'

How will that help?

'Only in this way can scientists try to map which processes in our brain are responsible for, say, bringing together information from different senses. Most philosophers and neuroscientists are still looking for that one holy grail, but we argue that we can actually only expect real progress when we stop talking about the consciousness.'

What new insights can the book bring?

'We have listed the most recent insights from both philosophical and neuroscientific research into consciousness and linked them together. There is no other book that actually integrates the insights from the two fields. We are not trying to convince the reader of any particular position or view on consciousness, who can form their own informed opinion after reading.'

This is an translation of the interview in Radboud Recharge