What is meant by āloko in the following sutta? I usually see it translated as "light". Thaanissaro translates as "illumination". I'd always just interpreted that as figurative, in the same way as cakkhuṃ/vision is figuratively understood in the same phrase below. However recently I'm wondering if it's meant literally as well, as visual light tends to manifest more brightly in developed meditators both perceived internally and even distinguishable by others as the meditator having unusually bright lustre to their physical body, or even some cases of visible halo around their head.
from SN 56.11 dhammacakkappavattana suttam, this phrase repeated 12 times for the 12 aspects of the 4 noble truths.
pubbe ananussutesu dhammesu cakkhuṃ udapādi, ñāṇaṃ udapādi, paññā udapādi, vijjā udapādi, āloko udapādi.
From DPR's composite dictionary entry:
Āloka [ā + lok, Sk. āloka] seeing, sight (obj. & subj.), i. e.
1. sight, view, look S ;iv.128 = Sn 763; A iii. 236 (āloke nikkhitta laid before one's eye). anāloka without sight, blind Miln 296 (andha +).
2. light A i. 164 (tamo vigato ā. uppanno) = It 100 (vihato); A ii. 139 (four lights, i.e. canda˚, suriya˚, agg˚, paññ˚, of the moon, sun, fire & wisdom); J ii 34; Dhs 617 (opp. andhakāra); VvA 51 (dīp˚).
3. (clear) sight, power of observation, intuition, in combn. with vijjā knowledge D ii.33 = S ii.7 = 105, cp. Ps ii.150 sq. (obhāsaṭṭhena, S A on ii.7).
4. splendour VvA 53; DvA 71.
-- kara making light, bringing light, n. light -- bringer It 108. -- karaṇa making light, illumining It 108. -- da giving light or insight Th 1, 3. -- dassana seeing light, i. e perceiving Th 1, 422. -- pharaṇa diffusing light or diffusion of light Vbh 334; Nett 89. -- bahula good in sight fig. full of foresight A iii.432. -- bhūta light J vi 459 -- saññā consciousness or faculty of sight or perception D iii.223; A ii.45; iii.93 -- saññin conscious of sight i. e. susceptible to sight or insight D iii.49; M iii.3; A ii 211; iii.92, 323; iv.437; v.207; Pug 69. -- sandhi "break for the light", a slit to look through, an opening a crack or casement Vin i.48 = ii.209 = 218; ii.172 iii.65; iv.47; J iv.310; PvA 24.