 A comparative notion of progress ‘\(g_{1}\) is better than \(g_{2}\)’ could be defined by requiring that both \(I(g_{1}) \gt I(g_{2})\) and \(P(g_{1}\mid e) \gt P(g_{2}\mid e)\), but most hypotheses would be incomparable by this requirement. By using the weight \(a\), formula (3) expresses a balance between two mutually conflicting goals of inquiry. It has the virtue that all partial answers \(g\) in \(D(B)\) are comparable with each other: \(g\) is better than \(g'\) if and only if the value of (3) is larger for \(g\) than for \(g'\). 