For example, because a thermometer is reliably causally connected to the world, when it reads 60 it means that the temperature is 60.
Similarly if an AI system is reliably causally connected to the world, its (syntactic) belief that egg foo young is in front of it will mean (semantically) that egg foo young  medically young is in front of it.
Note: for a similar argument, see "Causal connection with the world is essential to meaning", Box 8.