black-and-white thinking, false dichotomy, false dilemma

In the error in logic known as black-and-white thinking, the writer suggests that there are only two (or three) possible options when in fact there is a whole range of positions or choices. (It’s like seeing only in black and white and ignoring the shades of gray in between.)

• Those who are not with us are against us! [There are more than two possible positions. A person or group could have a neutral stance or could disagree in part with our position without entirely opposing us.]
• Environmental legislation will lead to job losses, because offending factories will have to be shut down. [Is shutting down factories the only solution to complying with the legislation?]
• You won’t fund my campaign for the protection of purple-crested warblers? How can you claim to be concerned about the environment? [Are there only two possible positions: on the one hand, willingness to fund a specific campaign; on the other, a total lack of concern for the environment?]

This error in thinking is also known as a false dilemma or a false dichotomy. (A dichotomy is a division of something into two opposing parts.)