The day when i first got my Mac I downloded Minecraft and when i tried to place a blcok it would not let me it would only let me destroy the block even if i right clicked or left clicked.
What I extected to happen was:
I was going to hit right click to place down the block/use the block, and hit left click to destory the block/item.
What actually happen was:
I hit right click to destory my tree then i crafted it into wodden planks and then i tried to place down the planks to bulid my house by left click
Please verify that:
In System Preferences > Mouse, the Primary Mouse Button is Left. If this is "Right" then the controls are expected to be reversed.
In Minecraft > Options > Controls, Attack/Destroy is Left Click and Use Item/Place Block is Right Click.