* Parallelism: The use of similar grammatical structures ("dangers... invasion... and... convulsions...") to create a sense of balance and emphasis. This makes the statement memorable and impactful.
* Antithesis: The contrast between "invasion from without" (external threat) and "convulsions within" (internal chaos) creates a stark opposition that highlights the severity of both dangers.
* Alliteration: The repetition of the "w" sound in "within" and "without" adds a sense of rhythm and reinforces the contrasting elements.
These devices work together to create a powerful and evocative statement that warns of both external and internal threats.