Breakdown of Ik zeg van wel, maar hij zegt van niet.
ik
I
hij
he / it (referring to a 'de'-word)
maar
but
zeggen
to say
Questions & Answers about Ik zeg van wel, maar hij zegt van niet.
Why do we use van wel and van niet here instead of just ja and nee?
After verbs of thought and communication like zeggen (to say), denken (to think), or hopen (to hope), Dutch uses van wel and van niet to refer back to a whole idea that was just mentioned. It acts as a substitute for a full clause. While English simply says "I say yes," Dutch essentially says "I say that it is so."
Could I just say Ik zeg ja, maar hij zegt nee?
You can, but it means something slightly different. Ik zeg ja means you are literally uttering the word "yes", for example when casting a vote. Ik zeg van wel means "I say that it is the case," referring back to a statement, debate, or situation rather than just quoting the word itself.
Why is it van niet instead of van nee?
Because you are substituting a full sentence, Dutch uses the adverb niet (not) rather than the exclamation nee (no). If the full unspoken sentence is "I say that he is not coming", you need niet to negate that action. Therefore, the set phrase is always van niet.
How does the word wel function in van wel?