«وَفِيهِ نَظَرٌ؛ لِأَنَّ كَوْنَ الشَّيْءِ نِسْبِيًّا لَا يَقْتَضِي تَعَسُّرَ تَحْقِيقِ مَعْنَاهُ»
There is an objection: a thing's being relative does not entail difficulty in defining its meaning.
Fatherhood and brotherhood are relational concepts, yet their meanings can be defined. Therefore a suitable comparative standard should be sought rather than assuming that relativity itself makes definition impossible.