Full Idea
'All A's are B's' meant for Frege that the concept A implies the concept B, or that to be A implies also to be B. Moreover this applies to arbitrary x which happens to be A.
Gist of Idea
For Frege, 'All A's are B's' means that the concept A implies the concept B
Source
report of Gottlob Frege (Begriffsschrift [1879]) by Michal Walicki - Introduction to Mathematical Logic History D.2
Book Reference
Walicki,Michal: 'Introduction to Mathematical Logic' [World Scientific 2012], p.23
A Reaction
This seems to hit the renate/cordate problem. If all creatures with hearts also have kidneys, does that mean that being enhearted logically implies being kidneyfied? If all chimps are hairy, is that a logical requirement? Is inclusion implication?