conjunction
as such; therefore; for that reason
Formal, literary conjunction used to introduce a logical consequence. Equivalent to modern したがって or それゆえに, but with a classical, written-register feel. Rare in everyday speech.
彼は証拠をすべて隠滅した。然るが故に、有罪は免れない。
He destroyed all the evidence. As such, he cannot escape conviction.
この書は古来より聖典とされてきた。しかるが故に、その解釈には細心の注意を要する。
This book has been regarded as sacred since ancient times. For that reason, its interpretation requires the utmost care.
Standard modern conjunction meaning 'therefore' or 'accordingly'. Used in both spoken and written Japanese, whereas 然るが故に is literary and archaic.
Also a formal/literary 'therefore', but more common than 然るが故に. それゆえに can appear in modern formal writing, while 然るが故に is distinctly classical.
Classical Japanese construction combining 然る (sikaru, 'to be so') + が (possessive/connective particle) + 故に (yueni, 'because of'). The phrase fossilized as a formal conjunction meaning 'for that reason'.