His position is ‘that either position or momentum are “as yet undetermined”’. That means that the ‘uncertainty’ is not due to our ability to measure things, but

His position is ‘that either position or momentum are “as yet undetermined”’. That means that the ‘uncertainty’ is not due to our ability to measure things, but ‘rather […] a statement about the actual reality about what variables (hidden or not) are stored by each particle’. :)