 This passage illustrates well how Łukasiewicz was thinking of logic in the early twenties. First, he was thinking in algebraic terms, rather than syntactically, concerning himself not so much with the construction of new systems, but with the evaluation of the systems relatively to sets of values. Secondly, he was introducing three-valued matrices to make logical space for the notion of propositions (eminently about future contingents) that are neither true nor false, and that receive the new indeterminate value ½. Ironically, later work employing his original matrix method will show that the hope of treating modal logic as a three-valued system cannot be realized. See also the SEP entry on  many-valued logic.