This quote by Lactantius speaks with the idea that fear and knowledge are incompatible. Fear is a feeling that can cause us to act in unreasonable ways, frequently causing choices that are not based upon wisdom. When we are in a state of worry, we are not able to think plainly and make choices that are based upon sound judgement. Worry can cause us to become overwhelmed and unable to believe rationally. In contrast, knowledge is the ability to make choices that are based upon knowledge and experience. It is the capability to think critically and make decisions that are in our benefit.
The quote by Lactantius recommends that when fear is present, it is difficult to make decisions that are based on knowledge. Fear can cause us to end up being overloaded and unable to think plainly, making it challenging to make decisions that remain in our benefit. Fear can likewise trigger us to end up being illogical and make choices that are not based on sound judgement. For that reason, when worry exists, it is impossible to make choices that are based upon wisdom.
