Projectivism
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Consider the sentence:
(1) Mary is a brunette.
This sentence attributes a property (dark-hairdness) to Mary. The sentence is true if and only if Mary has this property. Now consider by way of contrast the sentence:
(2) Mary is beautiful.
Prima facie, (2) has much the same character as (1). It attributes a property (beauty) to Mary. It is true if and only if Mary has this property.
But consider the proverb ‘Beauty is in the eye of the beholder’. On this common view, (2) and (1) are not as similar as they might first appear. If I utter (2), I am not so much attributing a property to Mary as I am characterising my own reaction to her. I say ‘Mary is beautiful’ since she evokes a certain reaction in me. I find her beautiful.
Such a view might be called ‘projectivist’: beauty is not a property of Mary. In describing her as beautiful I am ‘projecting’ my reaction onto her, talking as though my reaction to her is a property of her.
This is David Hume’s description of his projectivism:
'Tis a common observation, that the mind has a great propensity to spread itself on external objects, and to conjoin with them any internal impressions, which they occasion, and which always make their appearance at the same time that these objects discover themselves to the senses. (Hume, Treatise of Human Nature, I. iii. XIV)
These descriptions of projectivism are admittedly vague. Many forms of projectivism have been developed and it is not easy to give a formal definition. Rather, they bear family resemblances to one another, in Wittgenstein’s happy phrase.
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[edit] Projectivism in Aesthetics
Projectivism in aesthetics has already been discussed as an example. Most opponents of projectivism in aesthetics claim that beauty is a real objective property that some objects have and others lack.
[edit] Projectivism in Ethics
Hume (Treatise on Human Nature) is perhaps the grandfather of ethical projectivism, which was philosophical orthodoxy throughout the twentieth century. It has since fallen out of favour, but has some supporters, notably Simon Blackburn (Essays in Quasi-Realism, Spreading the Word).
Projectivism in ethics is associated by many with moral relativism, and is highly controversial.
[edit] Projectivism in the Theory of Colour
Optics and neurology have taught us a great deal about human colour perception. It has been claimed that modern science has undermined the naive idea that objects are coloured in the way we experience them. For example, there is no property of yellowness common to ripe bananas, lemons etc. We call all these things ‘yellow’ because they induce certain visual sensations in us, and we wrongly suppose that these experiences are properties of the objects themselves. See for example C H Hardin’s book Colour for Philosophers.
[edit] Hume's Projectivist theory of Causation
Suppose for example that somebody is hit by a hammer, and sometime later a bruise appears at the point of impact. The impact of the hammer is an observable event; the bruise too is observable. The causal connection between the two events, however, is not observed or experienced, at least according to Hume. Hume was led to doubt that causal connections are a real feature of the World. In particular, there is no causal connection between the impact of the hammer and the raising of the bruise. There are two unconnected events. We have however, observed on many occasions an impact and subsequent bruise. We are led by induction to suppose that each time the human body is hit hard, a bruise will rise. When we see somebody hit by a hammer we expect a bruise. It is this expectation, Hume claimed, that it projected into the world, and thought of as a causal connection.
In short: what we think of causal connections are really connections in our own thoughts that we suppose to be real features of the world.
Hume’s theory is not now widely held.
[edit] The Projectivist Theory of Probability
What does it mean to say that the probability that a coin lands heads is ½? One might think that the coin will either land upward or it will not, the probability is not a feature of the world, but rather just a measure of our own ignorance.
Frank Ramsey (see his collected papers, edited by D. H. Mellor) and Bruno de Finetti (citation needed), developed projectivist theories of probability in the early twentieth century. To explain their theories, the concept of degree of belief must first be introduced.
Let us say that a person has a degree of belief of 1 in a particular proposition if he completely convinced of its truth. For example, most people have a degree of belief of 1 in the proposition that 2+2=4. On the other hand, a person has a degree of belief 0 in a proposition if he is utterly convinced of its falsity; most people have a degree of belief of zero in the proposition that 2+2=5. Intermediate values are possible. A man who thinks that his dog has stolen the sausages, but is not completely sure, might have a degree of belief of 0.8 in the proposition that his dog stole the sausages.
For each person A, we can define a (partial) function CA mapping the set of propositions to the closed interval [0, 1] by stipulating that for a proposition P CA(P)=t if and only it C has a degree of belief t in the proposition P. Ramsey and de Finetti independently attempted to show that if A is rational, CA is a probability function: that is, CA satisfies the standard (Kolmogorov) probability axioms.
They supposed that when I describe an event has having probability P I am really voicing my degrees of belief. Probabilities are not real features of the world.
For example, when I say that the event that the coin lands heads up has probability ½, I do so because my degree of belief in the proposition that the coin will land heads up is ½.
