Indeed a very great deal of our knowledge is obtained from other persons - persons who were present at events at which we ourselves were not, persons who have more acute senses than the rest of us, etc. Heavier objects fall faster than light ones. If there are 5 persons in a room and none leave, then if 6 persons enter that room, there will be 11 persons in that room. To get greater fuel economy in a car, one should turn off the air-conditioning and open the windows. Everything that is colored is extended.
Nothing can be both red and blue all over at the same time in the same place.
Empiricists will deny of all the claims immediately above, and indeed of any and all others, that they are both contingent and knowable a priori. There are no innate concepts. But you'll have to examine the context of the argument to be sure.