4.1221 An internal property of a fact can also be bed a feature of that
fact (in the sense in which we speak of facial features, for example).


4.123 A property is internal if it is unthinkable that its object should
not possess it. (This shade of blue and that one stand, eo ipso, in the
internal relation of lighter to darker. It is unthinkable that these two
objects should not stand in this relation.) (Here the shifting use of the
word 'object' corresponds to the shifting use of the words 'property' and
'relation'.)


4.124 The existence of an internal property of a possible situation is not
expressed by means of a proposition: rather, it expresses itself in the
proposition representing the situation, by means of an internal property of
that proposition. It would be just as nonsensical to assert that a
proposition had a formal property as to deny it.


4.1241 It is impossible to distinguish forms from one another by saying
that one has this property and another that property: for this presupposes
that it makes sense to ascribe either property to either form.


4.125 The existence of an internal relation between possible situations
expresses itself in language by means of an internal relation between the
propositions representing them.