 So, if we assign "water" the primary intension "watery stuff", then the secondary intension of "water" is H2O, since H2O is "watery stuff" in this world.The secondary intension of "water" in our world is H2O, which is H2O in every world because unlike "watery stuff" it is impossible for H2O to be other than H2O.When considered according to its secondary intension, "Water is H2O" is true in every world.