  Texts like news, encyclopedias, and some social media strive for objectivity.
Yet bias in the form of inappropriate subjectivity - introducing attitudes via
framing, presupposing truth, and casting doubt - remains ubiquitous. This kind
of bias erodes our collective trust and fuels social conflict. To address this
issue, we introduce a novel testbed for natural language generation:
automatically bringing inappropriately subjective text into a neutral point of
view ("neutralizing" biased text). We also offer the first parallel corpus of
biased language. The corpus contains 180,000 sentence pairs and originates from
Wikipedia edits that removed various framings, presuppositions, and attitudes
from biased sentences. Last, we propose two strong encoder-decoder baselines
for the task. A straightforward yet opaque CONCURRENT system uses a BERT
encoder to identify subjective words as part of the generation process. An
interpretable and controllable MODULAR algorithm separates these steps, using
(1) a BERT-based classifier to identify problematic words and (2) a novel join
embedding through which the classifier can edit the hidden states of the
encoder. Large-scale human evaluation across four domains (encyclopedias, news
headlines, books, and political speeches) suggests that these algorithms are a
first step towards the automatic identification and reduction of bias.
