Error message - why does it say "object not found"?

Question

I'm very new to R and stackoverflow, so I apologize ahead of time if I'm breaking any etiquette somehow.

I have only typed a few lines of code so far, following a book tutorial. The book is Statistical Modeling: A Fresh Approach, printed in 2012, so I'm not sure what version of R it has. I am using R 4.0.0.

All I have written so far is:

cherryBlossom2008 <- read.csv("Cherry-Blossom-2008.csv")
names(cherryBlossom2008)

this produces:

[1] "position" "division" "total" "name" "age" "place" "net" "gun" "sex"

Next I typed:

mean(age, data=cherryBlossom2008)

I immediately get an error message that says:

Error in mean(age, data = cherryBlossom2008) : object 'age' not found

I'm not sure how this is possible. 'age' is in cherryBlossom2008. My book says that I would get that error message if I failed to define "data" when using the "mean" command, but as you can see I did define "data", so I don't understand how else I would define 'age'.