ACROSS
 1. (SEMI-RATIONALIST)* = ARISTOTELIANISM <philosophy>
 9. <lizard> GECKO = G_E_C_ + KO
10. <heading> NORTH-EAST = ANOTHER* ST
11. <apocalypse> RAGNAROK = ←KORAN← after RAG
12. P_L AS + MA = PLASMA <state>
14. A _L_ _I_ _T_ = ALIT <touched down>
15. PI RATES HIP = PIRATE SHIP = <transportation of criminals>
18. (OIL CAPITAL)* = APOLITICAL <unaffected by government>
19. _S IRE = SIRE <father>
21. <restaurant course> ENTREE = "ON TRAY"
23. <eye disease> GLAUCOMA = (A LOCUM)* inside GA
25. <impression> ENGRAVING = ENG RAVING
26. BALTI[-c] = BALTI <curry>
27. <WC> TUNGSTEN CARBIDE = (DISTURBANCE GENT)*

DOWN
 1. ME inside A N GERMAN AGENT = ANGER MANAGEMENT <self-control>
 2. IN COG "NEATO" = INCOGNITO <wearing camo>
 3. TAX outside H OR = THORAX <chest>
 4. TEN + DO ←SIT-IN← = TENDONITIS <joint issue>
 5. LO RE = LORE <information>
 6. <Greek hero> ACHILLES = HILL inside ACES
 7. I MAM S_ = IMAMS <clerics>
 8. <drug> METHAMPHETAMINE = MET HAM + (H inside PETA MINE)
13. PARA PIC outside LEG = PARAPLEGIC <immobile>
16. H OI OI outside POLL = HOI POLLOI <common people>
17. IDE inside SWAYS = SIDEWAYS <moving laterally>
20. L UMBER = LUMBER <planks of wood>
22. <cross> TIGON = TIG O_ N_
24. D_ + I'VE = DIVE <nightclub>