We would therefore argue that strength of character turns to obstinacy as soon as a man resists another point of view, not from some superior insight or attachment to some higher principle, but because he objects instinctively.

[Wir sagen also: die Charakterstärke wird zum Eigensinn, sobald das Widerstreben gegen fremde Einsicht nicht aus besserer Überzeugung, nicht aus Vertrauen auf einen höheren Grundsatz, sondern aus einem widerstrebenden Gefühl entsteht.]

Karl von Clausewitz (1780-1831) Prussian soldier, historian, military theorist

On War [Vom Kriege], Book 1, ch. 3 “On Military Genius [Der Kriegerische Genius],” (1.3) (1832) [tr. Howard & Paret (1976)]
    (Source)

(Source (German)). Alternate translations:

We say therefore, force of character degenerates into obstinacy whenever the resistance to opposing judgment proceeds not from better convictions or a reliance upon a more trustworthy maxim, but from a feeling of opposition.
[tr. Graham (1873)]

We say, therefore, strength of character becomes obstinacy as soon as resistance to an opposing judgment proceeds not from a better conviction or reliance upon a higher principle, but from a feeling of opposition.
[tr. Jolles (1943)]