Chapter 2: Towards a Theory of Declarative Knowledge
2.
A closed atom A is true in / iff A Ε /.
3.
A closed formula
—ι
S is true in / iff S is not true in /.
4.
A closed formula 3x.S is true in / iff for some variable free term t the
formula S(t/x) is true in /.
5.
A closed formula
VJC.S
is true in / iff (by (1)!) S is true in /.
6. A closed formula S
x
S
2
is true in / iff S
2
is not true in / or S
x
is true in /.
7.
A closed formula S.&.-.&S^ is true in / iff each of the 5, is true in /.
8. A closed formula S, V ... V S
m
is true in / iff one of the 5, is true in /.
1 m ι
9. A closed formula S
l
++S
2
is true in / iff (S
x
is true in / if and onl
Become an O’Reilly member and get unlimited access to this title plus top books and audiobooks from O’Reilly and nearly 200 top publishers, thousands of courses curated by job role, 150+ live events each month, and much more.