Praxis (DXHR)

Praxis Points are a hybrid system of skill points and augmentation canisters in Deus Ex: Human Revolution.

When Sarif Industries treats Adam Jensen's injuries after the opening sequence, he is fitted with every augmentation they have available. However, Adam cannot immediately utilize most of them due to a combination of inexperience and as-of-yet unhealed damage to his brain. As he heals and "praxises", they are activated at his preference.

As players progress through the game and gain experience points (XP), they are awarded Praxis points, which can then be used to activate dormant augmentations and upgrade active ones.

Typically, it costs 2 points to activate an augmentation, and 1 point for each subsequent upgrade. Players are awarded 1 Praxis point for every 5,000 experience points they collect as they progress, but points can also be obtained by purchasing Praxis kits at LIMB clinics or finding them in the world.

Experience
The player is awarded different amounts of XP by completing mission objectives, indicated by the Getting things done (Main quests) and Completionist (side-quests) bonuses. However, there are also some fixed XP bonuses awarded for certain actions:

Combat
Neutralizing an enemy is the most straight-forward way of actively earning XP. Different bonuses are awarded, depending on how the enemy is neutralized. The combat bonuses are cumulative. For example, a non-lethal takedown awards a total of 50 XP (Man Down + Merciful Soul + Expedient). However, the "Expedient" bonus is only counted once per takedown; a double non-lethal takedown only awards 125 XP: 2x Man Down (20 XP), 2x Merciful Soul (40 XP), Expedient (20 XP), Two Against One (45 XP), so effectively the bonus from double takedown as compared to two single takedowns is 25 XP.
 * Man Down (10 XP) — neutralize a human enemy.
 * Merciful Soul (20 XP) — neutralize a human enemy in a non-lethal way.
 * Marksman (10 XP) — neutralize an enemy with a headshot (the enemy can be headshot or even bodyshot several times, as long as the killing blow is a headshot. This can be a lethal or non-lethal weapon.)
 * Expedient (20 XP) — neutralize an enemy by performing a melee takedown.
 * Two Against one (45 XP) — neutralize two enemies with a single takedown (using the Reflex Booster aug).
 * Hunk of Junk (45/250 XP) — neutralize a small security bot or sentry (250 for boxguards).

Stealth
The player gets XP bonuses for completing storyline mission objectives through stealthy measures. Not every objective awards stealth bonuses. Smooth Operator bonus is not available for the objectives where no alarm-triggering equipment is present. Some of the objectives have two mutually exclusive ways to completing them, when getting Silver Tongue bonus will prevent the stealth bonuses from being awarded and vice versa. There are no stealth bonuses for any of the side-quests, although sometimes they have a stealthy completion as a secondary objective.
 * Ghost (500 XP) — complete an objective without enemies spotting the player or seeing the bodies of their downed allies.
 * Smooth Operator (250 XP) — complete an objective without setting off an alarm.

For more detailed information on these bonuses see their respective pages.

Hacking
For every security level there is an increasing bonus for successfully hacking a device. Additional Script Kiddie XP bonuses may also be awarded by capturing certain datastores during the hacking mini-game.
 * Script Kiddie (25 XP) — Level 1.
 * Grey Hat (50 XP) — Level 2.
 * Black Hat (75 XP) — Level 3.
 * L33t Sk1llz (100 XP) — Level 4.
 * Master Hacker (125 XP) — Level 5.

Exploration
By finding certain areas or taking routes other than the most obvious ones, the player is also awarded bonus XP. The first four bonuses are awarded by simply entering a certain area. The amount of XP awarded is tied to the specific area. Areas towards the end of the game tend to award the higher XP bonuses, but often require augmentations to reach (such as an air vent under the Tai Yong Medical building, which is too high to drop down without the Icarus Landing System).
 * Traveler (100 XP)
 * Explorer (200 XP)
 * Pathfinder (300 XP)
 * Trailblazer (400 XP)
 * Scholar (200 XP) — find and read one of the 29 unique eBooks.

Social
At some points in the game, the player will have to try to persuade an NPC in order to meet a certain objective. This triggers a persuasion mini-game where the CASIE mod can be of value. While these mini-games take quite a while to finish (the dialog cannot be skipped), they are usually worth the 1000 XP points alone (equivalent to 20 non-lethal take-downs).
 * Silver Tongue (1000 XP) — succeed in persuasion.
 * Life Lesson (100 XP) — fail the conversation.

Maximizing XP
Activating all augments requires 68 Praxis points. There are 21 Praxis kits in the game total available through exploration, from LIMB clinics and as side-quest rewards. This means that you need 47 additional points to unlock all available augmentations — a total of 235,000 experience points. Without the bonus mission from the Explosive Mission Pack DLC there is a maximum of 238,470 XP in the game and 241,970 XP with it, so in either case it is indeed possible to get all augmentations by the end of the game.

Tips for maxmizing XP (in order of impact):
 * 1) Complete main storyline mission objectives.
 * 2) Complete side mission objectives.
 * 3) Hack every single hackable device encountered, capturing any data stores.
 * 4) Explore the entire map for area bonuses and XP eBooks.
 * 5) Complete objectives while remaining undetected and without setting off any alarms.
 * 6) Neutralize all enemies, performing non-lethal takedowns (50 XP each). Try to take down two enemies at once whenever possible (62.5 XP each). Destroy turrets and bots.

A list of all obtainable experience point rewards can be found on Experience by area page.