This document presents an empiricist mentalist semantic theory that could be implemented computationally. It addresses three major objections to the original theory. The intersubjectivity objection is met with the proposal of webs of similar ideas within subjects. The self-applicability objection is addressed by conceiving of ideas as self-applying like coin slots. The abstract ideas objection is dealt with by suggesting ideas are pattern-like rather than image-like, analogous to regular expressions. Further research is needed to develop these proposals.

1. Empiricist Mentalist Semantics
Barry Nouwt
Master’s Thesis Cognitive Artificial Intelligence
Supervised by Dr. H.L.W. Hendriks
June 2008

2. Contents
• Introduction
• Intersubjectivity Objection
• Self-applicability Objection
• Abstract ideas Objection
• Conclusion
• Further Research / Discussion
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3. Introduction
• Computers can speak, read and hear
sentences
• Computers cannot understand meaning of
sentences
• Semantic theory to implement meaning
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4. Introduction
• Semantic theory from philosophy.
• Ludwig Wittgenstein and Gottlob Frege
are recent and popular.
• However, not suitable for implementation
because non-mentalist.
• Let’s look at less recent semantic theories!
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5. Introduction
• Mentalist Semantic theories from 17th
century.
• John Locke’s Empiricist Mentalist
Semantic Theory from his book An Essay
Concerning Human Understanding (1690).
• Seems more suitable for implementation
on computers.
• Let’s take it as our starting point!
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6. Introduction
• Three serious objections against
Empiricist Mentalist Semantic Theory
(EMST)
• Intersubjectivity Objection (Frege)
• Self-applicability Objection (Wittgenstein)
• Abstract Ideas Objection (Berkeley)
• How can these three objections be met?
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7. Intersubjectivity Objection
• Intersubjectivity: two subjects attribute the
same information to words (e.g. ‘tree’).
• Without intersubjectivity, communication is
impossible.
• Intersubjectivity and communicating
computers.
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8. Intersubjectivity Objection
“TREE”
I
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9. Intersubjectivity Objection
• Two subjects attribute the same
information to the word ‘tree’.
• Without intersubjectivity, communication is
impossible.
• Intersubjectivity and communicating
computers.
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10. Intersubjectivity Objection
• Gottlob Frege explains1 why EMST must
be incorrect: “It would be impossible for
something one man said to contradict
what another man said, because the two
would not express the same thought, but
each his own.”
1See Picardi (1996, Section ‘Frege’s anti-psychologism’)
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11. Intersubjectivity Objection
“TREE”
I
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12. Intersubjectivity Objection
“TREE”
I1 I2
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13. Intersubjectivity Objection
“TREE”
I1 I2
I1 ≠ I2
EMST 13/29

14. Intersubjectivity Objection
• Similarity plays a crucial role in meeting
the objection.
• Jonathan Lowe says1: “[I]t is hard to see
how there can be any intersubjective,
publicly available criterion for the similarity
of ideas occurring in two different minds.”
• We will suggest such a criterion.
1See Lowe (1995, p. 151)
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15. Intersubjectivity Objection
• Web-similarity criterion: Two ideas are
web-similar if and only if they are related
in the same way to other web-similar
ideas.
• This criterion assumes two webs-of-ideas
within two different subjects A and B.
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16. Intersubjectivity Objection
Web-of-ideas of Subject A Web-of-ideas of Subject B
4A 4B
Web-
similar
1A 1A = 1B 1B
3A 3B
2A 2B
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17. Intersubjectivity Objection
• Web-similarity = intersubjective, publicly
available criterion.
snowB
whiteA snowA blackB
“Snow is white”
whiteB
blackA
“Snow is black”
Subject A Subject B
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18. Self-Applicability Objection
• Application criteria: observable similarity.
• For example the idea ‘tree’.
• However, applying ideas to reality leads to
an infinite regress1 of interpreting the
interpretation of an interpretation, etc.
1See Lowe (1995, p.164) and Stokhof (2003, pp. 48-49)
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19. Self-Applicability Objection
Reality
Inside subject
?
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20. Self-Applicability Objection
• Only way out: ideas are self-applying.
• Wittgenstein and Stokhof1: self-applying
ideas are not plausible.
• Lowe2: self-applying ideas are plausible.
• Compare ideas with coin-slots in an
automatic vending machine.
1See Stockhof (2003, p. 40) and Wittgenstein (1958, p. 37)
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2See Lowe (1995, pp. 164-165)

21. 1 eurocent coins
10 eurocent coins
1 euro coins
Self-Applicability Objection
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22. Abstract-Ideas Objection
• According to John Locke1 the idea
‘triangle’: “must be neither Oblique, nor
Rectangle, neither Equilateral, Equicrural,
nor Scalenon; but all and none of these at
once.”
• That is: the idea ‘triangle’ must be
indeterminate with respect to certain
properties.
1See Locke (1690, Section IV.vii.9)
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23. Abstract-Ideas Objection
Idea ‘triangle’?
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24. Abstract-Ideas Objection
• Therefore1: “the idea of man I frame to my
self, must be either of a white, or a black,
or a tawny, a straight, or a crooked, a tall
or a low, or a middle-sized man.”
• Since image-like ideas cannot be
indeterminate, EMST is incorrect because
it cannot explain the existence of abstract
ideas.
1See Bennett (1971, p. 36)
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25. Abstract-Ideas Objection
• What if ideas are not image-like?
• Locke and others1 hint at ideas being
pattern-like, but do not elaborate.
• Maybe pattern-like ideas can be
indeterminate and represent all types of
triangles.
1See Lowe (1995, p. 156) and Locke (1690, Section III.iii.19 and
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Section III.iv.2)

26. Abstract-Ideas Objection
• Regular Expression = definition of a
pattern in strings of characters.
• For example:
– ^[a-z0-9._%+-]+@[a-z0-9.-]+.[a-z]{2,4}$
– “abcd012@abcd.ab”
– “johndoe@hotmail.co.uk”
– “this@is.not.a.match”
• Regular Expression can be indeterminate
with respect to certain properties.
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27. Abstract-Ideas Objection
• Suggestion: Similar pattern definitions only
not for strings of characters.
• Just like RegEx, can these patterns be
indeterminate with respect to certain
properties.
• These patterns might be able to represent
all types of triangles.
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28. Conclusion
• Intersubjectivity Objection:
– Web-of-ideas
– Web-similarity
• Self-Applicability Objection:
– Ideas are slot-like (as coin-slots in vending
machines)
• Abstract-Ideas Objection:
– Ideas are pattern-like (analogous to RegEx)
• Updated EMST is just a first step!
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29. Further Research / Discussion
• Web-of-ideas: Is it plausible and what are
their properties?
• Slot-like ideas: Are they compatible with
current knowledge about the brain?
• Pattern-like ideas: Are they powerful
enough to account for meanings of all
words?
• Web-of-ideas: What is their relation to
semantic structures?
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30. Semantic Structure
Source: http://www.carp-technologies.nl/nld/images/stories/q&a/sem2.gif 30/29