Unification and Understanding. Victor Gijsbers Universiteit Leiden

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1 Unification and Understanding Victor Gijsbers Universiteit Leiden

2 Three concepts

3 Explanation and determination To explain is to show how certain facts hang together. To be more precise, an explanation shows how the explanans determined the explanandum. For instance: to explain why the window broke, we give the causal antecedents (a ball being thrown at a certain angle and with a certain momentum, the window having a certain strength) together with the causal laws that show that given these antecedents, the breaking had to occur.

4 Explanation and determination Many interesting questions here: are all explanations contrastive, do we need necessity or is raising the probability enough, and so on. One thing is clear: we need extra conditions on the notion of determination. Lawhood (Hempel): We [explain] when we can demonstrate that in the given circumstances the phenomenon follows from the laws of physics (Gerard Nienhuis, yesterday)

5 Explanation and determination Causation (Salmon, Woodward, Strevens) Good! (Even though we need to generalise it.) Unification (Friedman, Kitcher, Schurz & Lambert) Bad! (Because it doesn't work.)

6 Explanation and unification The idea of unificationism: we explain E if and only if we deduce E from a unifying theory. So Newton's theory explains the falling of this apple, because we can show that the apple will fall using the theory and the theory also allows us to deduce many other phenomena from the falling of other apples to the movement of the planets.

7 Explanation and unification Different authors have different definitions of unification. Perhaps the best and easiest to understand is that of Schurz and Lambert: a theory is unifying if it leaves fewer statements in the set of all our scientific knowledge as basic (= underived) than its competitors. Making this precise is rather technical, but we won't bother with that.

8 Explanation and unification But is it true? Couldn't we have explanation without unification? Example 1: Galileo's explanation of the phases of Venus. Example 2: Conference poster.

9 Explanation and unification Local connectedness versus global connectedness: only the former is necessary for explanation. So why did anyone think that unification and explanation had something to do with each other? Epistemic reasons to prefer unification. Quantity versus quality of explanation. But... something more?

10 Three concepts

11 Understanding without Expl. Several suggestions for understanding without explanation: Non-linguistic understanding / understanding through use. (Lipton) Understanding through intelligible theories. (Dieks & de Regt) Understanding through Kuhnian exemplars. (Lipton) Understanding through successful classification.

12 Lipton (I) Images, physical models, manipulations. Non-linguistic understanding? (Versus explanations, which are always linguistic.) Understanding through being able to use something practical understanding?

13 Dieks & De Regt A phenomenon is scientifically understandable iff there is an accepted intelligible scientific theory that saves it. A scientific theory T is intelligible for scientists (in context C) if they can recognise qualitatively characteristic consequences of T without performing exact calculations. Intelligibility is the value that scientists attribute to the... virtues (of a theory...) that facilitate the use of the theory for the construction of models.

14 Lipton (II) Understanding through Kuhnian examplars. [E]xemplars set up perceived similarity relations, and normal scientists attempt solutions that seem similar to those that worked in the exemplars... [T]hese abilities correspond also to a knowledge that goes beyond the explicit content of the theory. The exemplars provide knowledge of how different phenomena fit together.

15 Classification Both previous examples of understanding through explanation can be seen as forms of understanding through successful classification. Example: (pre-darwinian) classification of organisms. Knowledge and understanding, but not explanation.

16 Classification Understanding is the cognitive achievement realizable by scientists through their ability to coordinate theoretical and embodied knowledge that apply to a specific phenomenon. (Leonelli) By the verb coordinate, I mean strategies that a scientist can learn to use in order to (1) select beliefs that are relevant to the phenomenon in question, and (2) integrate these components with the goal of applying them to the phenomenon.

17 Understanding and Unification? We can understand phenomena by knowing where they fit into the scheme of nature a knowledge that can be theoretically expressed or embodied in skills of the subject. But fitting things into a scheme sounds a lot like unification!

18 Understanding and Unification! Unifying theories are precisely the theories that can give us powerful exemplars, that the scientist can learn to use quantitatively, that allow us to understand phenomena by giving them a place in a larger scheme of classification. But they perform this understanding-enhancing function independently of any capacity to explain, as the example of the classification of organisms shows.

19 Conclusion There are at least two kinds of understanding: Understanding the vertical hanging together of phenomena by seeing how they determine each other. It is given by explanation; the corresponding skills are causal or quasi-causal reasoning, and prediction. Understanding the horizontal hanging together of phenomena by seeing how they fit into a successful classification. It is given by unification; the corresponding skills are classifying and constructing models.

Key Ideas. Explain how science is different from other forms of human endeavor. Identify the steps that make up scientific methods.

Key Ideas. Explain how science is different from other forms of human endeavor. Identify the steps that make up scientific methods. Key Ideas Explain how science is different from other forms of human endeavor. Identify the steps that make up scientific methods. Analyze how scientific thought changes as new information is collected.