"Alles hat ein Ende, nur die Wurst hat zwei."

When the farmer went out and saw a black white shape he couldn´t know that there is is cow Doris.
Perhaps he could know that there is a cow but probably it can be even a trick and actually there is a black and white coloured paper or something else.
But sure is he really can´t know if his favourite cow is there. I may be can expect it may be he has only one cow on this field but it is possible that there is an other cow.
All in all he believed it that his cow is there.

The second passage:

It was right that the cow was there but like I wrote already he only saw a paper with the same colours. Actually the cow was outside but still there.
But farmer Richard was wrong as he said he know that the cow is there because actually she is outside in the hole for a nap.