Taduparaga apeksitvdt cittasya vastu jnata ajnatam

The seventeenth yoga sutra states about the capability of a conscious mind and a conditioned mind in regard to perceiving an object. It should always be kept in mind that consciousness is not the seer, but an instrument of the seer. A conditioned mind can never see an object in its true light; the mind in such instances has already been influenced upon, it is already biased and prejudiced. An object is known only upto that limit, which the mind wants to perceive, and in this process it remains un-perceived. A true yogi is the one, who has perceived the object in its truest light, staying un-distorted and has thus achieved enlightenment.

tad thereby
uparaga conditioning, colouring
apeksitvat expectation, hope, desire, want, need
cittasya by the consciousness, for the consciousness
vastu object
jnata known
ajnatam unknown

An object remains known or unknown according to the conditioning or expectation of the consciousness.

Consciousness is not the seer, but an instrument of the seer. A conditioned mind can never perceive an object correctly. If the mind sees the object without expectation, it remains free.

An object is understood and known according to the expectation of the mind, or remains unrecognized, owing to the absence of reflection. When the object attracts the mind, contact and reflection begin. This gives rise to knowledge. If the mind fails to come in contact with the object, it does not perceive it and the object remains unknown.

If consciousness is conditioned or coloured (vrttis and Mesas - 1.6 and 11.6), knowledge of the object also becomes coloured. When the consciousness reflects on the object without condition, taint or expectation, its real essence is known. Likewise, if the consciousness reflects on the essence of the seer without conditioning, bias, or prejudice, the mind becomes enlightened. It knows that it is not itself the seer, but only an instrument of the seer. The un-enlightened mistake mind and consciousness for the seer.