diff --git a/prototype/Doubt/Location.swift b/prototype/Doubt/Location.swift
index 240725407..f812006ea 100644
--- a/prototype/Doubt/Location.swift
+++ b/prototype/Doubt/Location.swift
@@ -24,7 +24,7 @@ public struct Location<A>: SequenceType {
 
 	public var into: Location? { return _into(it) }
 
-	public var up: Location? { return _up(it) }
+	public var outOf: Location? { return _up(it) }
 
 	public var left: Location? { return _left(it) }
 
@@ -32,7 +32,7 @@ public struct Location<A>: SequenceType {
 
 	/// The root `Location` in the current exploration.
 	public var root: Location {
-		return up?.root ?? self
+		return outOf?.root ?? self
 	}
 
 
@@ -43,7 +43,7 @@ public struct Location<A>: SequenceType {
 
 	/// Returns the logically next `Location` after the receiver and its children in a pre-order depth-first traversal.
 	private var nextAfter: Location? {
-		return right ?? up?.nextAfter
+		return right ?? outOf?.nextAfter
 	}
 
 
diff --git a/prototype/DoubtTests/LocationTests.swift b/prototype/DoubtTests/LocationTests.swift
index 4f939d842..068969e1b 100644
--- a/prototype/DoubtTests/LocationTests.swift
+++ b/prototype/DoubtTests/LocationTests.swift
@@ -4,7 +4,7 @@ final class LocationTests: XCTestCase {
 	}
 
 	func testCannotMoveUpwardsAtTheStartOfAnExploration() {
-		assert(term.explore().up?.it, ==, nil)
+		assert(term.explore().outOf?.it, ==, nil)
 	}
 
 	func testCannotMoveSidewaysAtTheStartOfAnExploration() {
@@ -21,7 +21,7 @@ final class LocationTests: XCTestCase {
 	}
 
 	func testCanMoveBackUpwards() {
-		assert(term.explore().into?.up?.it, ==, term)
+		assert(term.explore().into?.outOf?.it, ==, term)
 	}
 
 	func testCannotMoveLeftwardsFromFirstChildOfBranch() {
@@ -37,7 +37,7 @@ final class LocationTests: XCTestCase {
 	}
 
 	func testCanMoveBackUpwardsFromDeepExplorations() {
-		assert(term.explore().into?.right?.right?.into?.right?.up?.up?.it, ==, term)
+		assert(term.explore().into?.right?.right?.into?.right?.outOf?.outOf?.it, ==, term)
 	}
 
 	func testCanReturnToStartOfExplorationFromArbitrarilyDeepNodes() {
@@ -49,11 +49,11 @@ final class LocationTests: XCTestCase {
 	}
 
 	func testModifyReplacesSubtrees() {
-		assert(term.explore().into?.modify(const(leafB)).right?.up?.it, ==, Cofree(0, .Indexed([ leafB, leafB, keyed ])))
+		assert(term.explore().into?.modify(const(leafB)).right?.outOf?.it, ==, Cofree(0, .Indexed([ leafB, leafB, keyed ])))
 	}
 
 	func testMultipleModificationsReplaceMultipleSubtrees() {
-		assert(term.explore().into?.modify(const(leafB)).right?.modify(const(leafA)).up?.it, ==, Cofree(0, .Indexed([ leafB, leafA, keyed ])))
+		assert(term.explore().into?.modify(const(leafB)).right?.modify(const(leafA)).outOf?.it, ==, Cofree(0, .Indexed([ leafB, leafA, keyed ])))
 	}
 
 	func testModificationsPreserveKeys() {