Samkhya Karika 15, 16

भेदानां परिमाणात्, समन्वयात्, शक्तितः प्रवृत्तेश्च ।
कारणकार्यविभागात्, अविभागाद्वैश्वरूप्यस्य ॥ १५ ॥

bhedānāṁ parimāṇāt, samanvayāt, śaktitaḥ pravṛtteśca ।
kāraṇakāryavibhāgāt, avibhāgādvaiśvarūpyasya ॥ 15 ॥

bhedānāṁ=of specific objects; parimāṇāt=due to finite nature; samanvayāt=homogeneity; śaktitaḥ=due to power (efficiency); pravṛtteḥ=of the evolution; ca=and; kāraṇa=cause; kārya=effect; vibhāgāt=due to differentiation; avibhāgāt=unity (non-differentiation); vaiśvarūpyasya=of the universe (manifest world)

The unmanifest cause exists because of 1) the finite nature of special objects; 2) homogeneity; 3) evolution being due to the efficiency (power) of the cause; 4) the differentiation between cause and effect; 5) the non-differentiation or merging of the whole world of effects

कारणमस्त्यव्यक्तं प्रवर्तते त्रिगुणतः समुदयाच्च ।
परिणामतः सलिलवत् प्रतिप्रतिगुणाश्रयविशेषात् ॥ १६ ॥

kāraṇamastyavyaktaṁ pravartate triguṇataḥ samudayācca ।
pariṇāmataḥ salilavat pratipratiguṇāśrayaviśeṣāt ॥ 16 ॥

Kāraṇam=cause; asti=is, exists; avyaktaṁ=unmanifest (Mula Prakriti); pravartate=functions; triguṇataḥ=in respect of the three gunas (sattva, rajas, tamas); samudayāt=collectively; ca=and; pariṇāmataḥ=through modification; salilavat=like water; pratiprati=each (of the gunas); guṇāśraya=dominance of the guna; viśeṣāt=from the effects;

(cont. from previous verse) 6) its operation through the three gunas by combination and modification, like water, through differences arising from diverse nature of the several receptacles of the gunas.

In karika 14, it was stated that the presence of the Unmanifest is established since the effect is always of the nature of the cause. In karikas 15 and 16, further details of the same concept are provided. These karikas offer six reasons are presented to establish the presence of the cause, the Unmanifest.

1. bhedānāṁ parimāṇāt (due to the finite nature of the 23 tattvas): All the elements in the manifest world are finite or limited in nature. That means they are limited in terms of time and space. The clay pot produced by the potter is finite; however, as mentioned in a previous karika, the clay pot was inherent in the cause, the lump of clay. By extending this train of thought all the way back to the intellect, we recognize that the finite intellect was inherent in its cause, the Mula Prakriti.
2. samanvayāt (due to homogeneity): All the elements are known to have the three gunas – sattva, rajas, and tamas – as common constituents. As such, they all have the common properties of pleasure, pain and delusion. Gaudapada gives the example that when we see a boy performing sacred, spiritual rituals, we infer that he was born in a Brahmana family. Similarly, the elements having the three gunas must have been produced from the unmanifest which also is associated with the three gunas.
3. śaktitaḥ pravṛtteḥ (evolution due to the efficiency of the cause): Only when the cause has the capability can an effect happen. A common example is that mustard oil can be produced only from mustard seed. In the same manner, the creation of the 23 elements of the Manifest can only happen because of the presence of the efficient cause, the Mula Prakriti.
4. kāraṇakāryavibhāgāt (due to differentiation between cause and effect): a clay pot is different from its cause, the lump of clay; a gold bangle is different from its cause, gold. The five elements – earth, water, fire, air and ether – emerge and are different from their cause, the five tanmatras (sense of touch, smell etc.). The tanmatras are the effect of and different from their cause, the ego (ahamkara). Ahamkara is caused by and different from the intellect (buddhi) and the buddhi is caused by is different from the Mula Prakriti.
5. avibhāgādvaiśvarūpyasya (merging back of the manifest world): At the time of dissolution, all the elements merge back into their respective causes. The pot of clay and the gold bangle merge back into lump of clay and gold. Similarly, the five elements merge back into the five tanmatra, the tanmatras into the ego, the ego into the Mahat (intellect) and the intellect into the Mula Prakriti.
6. triguṇataḥ samudayāt (through the combination and modification of the three gunas): The gunas combine together to produce the effects. At every moment one of the three gunas dominates. The other two gunas support the dominant guna so the desired effect can be produced. For example, when the rajas dominates with larger support from tamas, the mind may engage in negative, destructive thoughts. On the other hand, when sattva dominates with more support from rajas, the mind would have positive, creative thoughts.
7. salilavat pratipratiguṇāśrayaviśeṣāt (like water taking on the shape of the respective receptacle): The same rain water can assume the shape of a cup, or a large ocean; moreover, depending upon where the water falls, it can have a different taste like sweet, sour etc.