"Definition of Truth" for sentences in System G (Myro, p. 408, in PGRICE)

Myro:

"These will, in general,

be true with respect to a

model AT SOME TIMES BUT

NOT AT OTHERS. This is, of course,

just what we should expect. For

'the wood is in the market-place'

(temporally unqualified) is true

TODAY but was false a year ago. Sentences

of System G, on the other hand,

will, as one should expect, retain

the SAME truth-value at all times, just

as (read tenselessly) 'In year k, the

wood is in the market-place' does not

change its truth-value over time."