Chain-of-Though (CoT) prompting has shown promising performance in various
reasoning tasks. Recently, Self-Consistency \citep{wang2023selfconsistency}
proposes to sample a diverse set of reasoning chains which may lead to
different answers while the answer that receives the most votes is selected. In
this paper, we propose a novel method to use backward reasoning in verifying
candidate answers. We mask a token in the question by ${\bf x}$ and ask the LLM
to predict the masked token when a candidate answer is provided by \textit{a
simple template}, i.e., ``\textit{\textbf{If we know the answer of the above
question is \{a candidate answer\}, what is the value of unknown variable ${\bf
x}$?}}'' Intuitively, the LLM is expected to predict the masked token
successfully if the provided candidate answer is correct. We further propose
FOBAR to combine forward and backward reasoning for estimating the probability
of candidate answers. We conduct extensive experiments on six data sets and
three LLMs. Experimental results demonstrate that FOBAR achieves
state-of-the-art performance on various reasoning benchmarks.

提出了一种结合前向和后向推理的新方法，称为 FOBAR，通过用简单模板生成问题并要求 LLM 预测被掩码的标记来验证候选答案，实验证明 FOBAR 在各种推理基准上达到了最先进的性能。