Karika 19

तस्माच्च विपर्यासात् सिद्धं साक्षित्वमस्य पुरुषस्य। कैवल्यं माध्यस्थ्यं द्रष्टृत्वमकर्तृभावश्च ॥१९॥

tasmācca viparyāsāt siddhaṁ sākṣitvamasya puruṣasya। kaivalyaṁ mādhyasthyaṁ draṣṭr̥tvamakartr̥bhāvaśca ॥19॥

[तस्मात् च विपर्यासात् सिद्धं साक्षित्वम् अस्य पुरुषस्य। कैवल्यं माध्यस्थ्यं द्रष्टृत्वम् अकर्तृ भावः च॥
tasmāt = from that (the multiplicity of purusha); ca = and / as well; viparyāsāt = deformities (of three qualities referred previously); siddhaṁ = is established; sākṣitvam = the witness; asya = of; puruṣasya = the purusha's; kaivalyaṁ = eligibility to liberation; mādhyasthyaṁ = intermediary nature; draṣṭr̥tvam = observer nature; akartr̥ = not the doer; bhāvaḥ = feeling / properties; ca = and / as well;]

Based on that (multiplicity of beings) and deformations (of three qualities) we can establish the Purusha as a witness. It also establishes the Purusha's eligibility to liberation, intermediary nature, the observer, and not the doer feeling.